Enalapril formulations

ABSTRACT

Provided herein are stable enalapril oral liquid formulations. Also provided herein are methods of using enalapril oral liquid formulations for the treatment of certain diseases including hypertension, heart failure and asymptomatic left ventricular dysfunction.

CROSS-REFERENCE OF RELATED APPLICATIONS

This application is a Continuation application of U.S. patentapplication Ser. No. 15/081,603, filed Mar. 25, 2016, which claims thebenefit of U.S. Provisional Patent Application No. 62/310,198, filedMar. 18, 2016, all of which are incorporated herein by reference intheir entirety.

BACKGROUND OF THE INVENTION

Hypertension, or high blood pressure, is a serious health issue in manycountries. According to the National Heart Blood and Lung Institute, itis thought that about 1 in 3 adults in the United States alone havehypertension. Left unchecked, hypertension is considered a substantialrisk factor for cardiovascular and other diseases including coronaryheart disease, myocardial infarction, congestive heart failure, strokeand kidney failure. Hypertension is classified as primary (essential)hypertension or secondary hypertension. Primary hypertension has noknown cause and may be related to a number of environmental, lifestyleand genetic factors such as stress, obesity, smoking, inactivity andsodium intake. Secondary hypertension can be caused by drug or surgicalinterventions, or by abnormalities in the renal, cardiovascular orendocrine system.

A number of antihypertensive drugs are available for treatinghypertension. Various therapeutic classes of antihypertensive drugsinclude alpha-adrenergic blockers, beta-adrenergic blockers,calcium-channel blockers, hypotensives, mineralcorticoid antagonists,central alpha-agonists, diuretics and rennin-angiotensin-aldosteroneinhibitors which include angiotensin II receptor antagonists (ARB) andangiotensin-converting enzyme (ACE) inhibitors. Angiotensin-convertingenzyme (ACE) inhibitors inhibit angiotensin-converting enzyme (ACE), apeptydyl dipeptidase that catalyzes angiotension I to angiotension II, apotent vasoconstrictor involved in regulating blood pressure.

Enalapril is a prodrug belonging to the angiotensin-converting enzyme(ACE) inhibitor of medications. It is rapidly hydrolyzed in the liver toenalaprilat following oral administration. Enalaprilat acts as a potentinhibitor of ACE. The structural formulae of enalapril and enalaprilatare as follows:

Enalapril is currently administered in the form of oral tablets, (e.g.,Vasotec®) or in the form of liquid formulations obtained byreconstitution of enalapril powder formulations. In addition to thetreatment of hypertension, enalapril tablets have been used forsymptomatic congestive heart failure, and asymptomatic left ventriculardysfunction.

SUMMARY OF THE INVENTION

Provided herein are enalapril oral liquid formulations. In one aspect,the enalapril oral liquid formulation, comprises (i) enalapril or apharmaceutically acceptable salt or solvate thereof; (ii) a sweetenerthat is sucralose (iii) a buffer comprising citric acid (iv) apreservative that is sodium benzoate and (v) water; wherein the pH ofthe formulation is less than about 3.5; and wherein the formulation isstable at about 5±3° C. for at least 12 months.

In some embodiments, the enalapril is enalapril maleate. In someembodiments, the formulation further comprises a flavoring agent. Insome embodiments, the buffer in the formulation further comprises sodiumcitrate dihydrate. In some embodiments, the amount of enalapril or apharmaceutically acceptable salt or solvate thereof is about 0.6 toabout 1.2 mg/ml. In some embodiments, the amount of sucralose is about0.5 to about 0.9 mg/ml. In some embodiments, the amount of citric acidin the buffer is about 0.8 to about 3.5 mg/ml. In some embodiments, theamount of sodium citrate dihydrate in the buffer is about 0.1 to about0.80 mg/ml. In some embodiments, the amount of the sodium benzoate isabout 0.2 to about 1.2 mg/ml. In some embodiments, the amount ofenalapril or a pharmaceutically acceptable salt or solvate thereof isabout 10 to about 25% (w/w of solids). In some embodiments, the amountof sucralose is about 8 to about 18% (w/w of solids). In someembodiments, the amount of citric acid in the buffer is about 17 toabout 47% (w/w of solids). In some embodiments, the amount of sodiumcitrate dihydrate in the buffer is about 1 to about 11% (w/w of solids).In some embodiments, the amount of sodium benzoate is about 12 to about25 (w/w of solids). In some embodiments, the pH of the formulation isbetween about 3 and about 3.5. In some embodiments, the pH of theformulation is about 3.3. In some embodiments, the citrate concentrationin the buffer is about 5 mM to about 20 mM. In some embodiments, thecitrate concentration in the buffer is about 10 mM. In some embodiments,the formulation is stable at about 5±3° C. for at least 18 months. Insome embodiments, the formulation is stable at about 5±3° C. for atleast 24 months. In some embodiments, the formulation does not containmannitol. In some embodiments, the formulation does not contain silicondioxide.

In one aspect, the enalapril oral liquid formulation, comprises (i)about 1 enalapril maleate; (ii) about 0.70 mg/ml of a sweetener that issucralose; (iii) a buffer comprising about 1.82 mg/ml citric acid; (iv)about 1 mg/ml of a preservative that is sodium benzoate; and (v) water;wherein the pH of the formulation is less than about 3.5; and whereinthe formulation is stable at about 5±3° C. for at least 12 months.

In some embodiments, the formulation further comprises a flavoringagent. In some embodiments, the buffer further comprises about 0.15mg/mL sodium citrate dihydrate. In some embodiments, the pH of theformulation is between about 3 and about 3.5. In some embodiments, thepH of the formulation is about 3.3. In some embodiments, the citrateconcentration in the buffer is about 5 mM to about 20 mM. In someembodiments, the citrate concentration in the buffer is about 10 mM. Insome embodiments, the formulation is stable at about 5±3° C. for atleast 18 months. In some embodiments, the formulation is stable at about5±3° C. for at least 24 months. In some embodiments, the formulationdoes not contain mannitol. In some embodiments, the formulation does notcontain silicon dioxide.

In one aspect, the enalapril oral liquid formulation comprises (i) about19.3% (w/w of solids) enalapril maleate; (ii) about 13.5% (w/w ofsolids) of a sweetener that is sucralose; (iii) a buffer comprisingabout 35.2% (w/w of solids) citric acid; (iv) about 19.3% (w/w ofsolids) of a preservative that is sodium benzoate; and (v) water;wherein the pH of the formulation is less than about 3.5; and whereinthe formulation is stable at about 5±3° C. for at least 12 months.

In some embodiments, the formulation further comprises a flavoringagent. In some embodiments, the buffer further comprises about 2.9% (w/wof solids) sodium citrate dihydrate. In some embodiments, the pH of theformulation is between about 3 and about 3.5. In some embodiments, thepH of the formulation is about 3.3. In some embodiments, the citrateconcentration in the buffer is about 5 mM to about 20 mM. In someembodiments, the citrate concentration in the buffer is about 10 mM. Insome embodiments, the formulation is stable at about 5±3° C. for atleast 18 months. In some embodiments, the formulation is stable at about5±3° C. for at least 24 months. In some embodiments, the formulationdoes not contain mannitol. In some embodiments, the formulation does notcontain silicon dioxide.

In one aspect, the enalapril oral liquid formulation consistsessentially of (i) about 1 mg/nil enalapril maleate; (ii) about 0.70mg/nil of a sweetener that is sucralose; (iii) a buffer comprising about1.82 mg/ml citric acid and about 0.15 mg/ml sodium citrate dihydrate;(iv) about 1 mg/ml of a preservative that is sodium benzoate; (v) aflavoring agent; and (vi) water; wherein the pH of the formulation isless than about 3.5 adjusted by sodium hydroxide or hydrochloric acid;and wherein the formulation is stable at about 5±3° C. for at least 12months.

Also provided herein are methods of treating hypertension in a subjectcomprising administering to that subject a therapeutically effectiveamount of enalapril oral liquid formulation comprising (i) about 1 mg/mlenalapril maleate; (ii) about 0.7 mg/ml sucralose; (iii) a buffercomprising about 1.82 mg/ml citric acid and about 0.15 mg/ml sodiumcitrate dihydrate; (iv) about 1 mg/ml of a preservative that is sodiumbenzoate; and (v) water; wherein the pH of the formulation is less thanabout 3.5; and wherein the formulation is stable at about 5±3° C. for atleast 12 months. In some embodiments, the formulation does not containmannitol. In some embodiments, the formulation does not contain silicondioxide.

In some embodiments, the hypertension is primary (essential)hypertension. In some embodiments, the hypertension is secondaryhypertension. In some embodiments, the subject has blood pressure valuesgreater than or equal to 140/90 mmm Hg. In some embodiments, the subjectis an adult. In some embodiments, the subject is elderly. In someembodiments, the subject is a child. In some embodiments, theformulation is administered to the subject in a fasted state. In someembodiments, the formulation is administered to the subject in a fedstate. In some embodiments, the formulation is further administered incombination with an agent selected from the group consisting ofdiuretics, beta blockers, alpha blockers, mixed alpha and beta blockers,calcium channel blockers, angiotensin II receptor antagonists, ACEinhibitors, aldosterone antagonists, and alpha-2 agonists.

Also provided herein are methods of treating prehypertension in asubject comprising administering to that subject a therapeuticallyeffective amount of enalapril oral liquid formulation comprising (i)about 1 mg/ml enalapril maleate; (ii) about 0.7 mg/ml of a sweetenerthat is sucralose; (ii) a buffer comprising about 1.82 mg/ml citric acidand about 0.15 mg/ml sodium citrate dihydrate; (iv) about 1 mg/ml of apreservative that is sodium benzoate; and (v) water; wherein the pH ofthe formulation is less than about 3.5; and wherein the formulation isstable at about 5±3° C. for at least 12 months. In some embodiments, theformulation does not contain mannitol. In some embodiments, theformulation does not contain silicon dioxide.

In some embodiments, the subject has blood pressure values of about120-139/80-89 mm Hg.

Also provided herein are methods of treating heart failure in a subjectcomprising administering to that subject a therapeutically effectiveamount of enalapril oral liquid formulation comprising (i) about 1mg/nil enalapril maleate; (ii) about 0.70 mg/ml of a sweetener that issucralose; a buffer comprising about 1.82 mg/ml citric acid and about0.15 mg/ml sodium citrate dihydrate; (iv) about 1 mg/ml of apreservative that is sodium benzoate; and (v) water; wherein the pH ofthe formulation is less than about 3.5; and wherein the formulation isstable at about 5±3° C. for at least 12 months. In some embodiments, theformulation does not contain mannitol. In some embodiments, theformulation does not contain silicon dioxide.

Also provided herein are methods of treating left ventriculardysfunction in a subject comprising administering to that subject atherapeutically effective amount of enalapril oral liquid formulationcomprising (i) about 1 mg/ml enalapril maleate; (ii) about 0.7 mg/ml ofa sweetener that is sucralose; (iii) a buffer comprising about 1.82mg/ml citric acid and about 0.15 mg/ml sodium citrate dihydrate; (iv)about 1 mg/ml of a preservative that is sodium benzoate; and (v) water;wherein the pH of the formulation is less than about 3.5, and whereinthe formulation is stable at about 5±3° C. for at least 12 months. Insome embodiments, the formulation does not contain mannitol. In someembodiments, the formulation does not contain silicon dioxide.

INCORPORATION BY REFERENCE

All publications, patents, and patent applications mentioned in thisspecification are herein incorporated by reference to the same extent asif each individual publication, patent, or patent application wasspecifically and individually indicated to be incorporated by reference.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of the invention are set forth with particularity inthe appended claims. A better understanding of the features andadvantages of the present invention will be obtained by reference to thefollowing detailed description that sets forth illustrative embodiments,in which the principles of the invention are utilized, and theaccompanying drawings of which:

FIG. 1: Effect of pH on degradant formation after 8 weeks of storage ofvarious enalapril solution formulations at 5° C.

FIG. 2: Effect of pH on degradant formation after 8 weeks of storage ofvarious enalapril solution formulations at room temperature (19-22° C.).

DETAILED DESCRIPTION OF THE INVENTION

Provided herein are stable enalapril oral liquid formulations. Alsoprovided herein are stable enalapril powder formulations forreconstitution for oral liquid administration. These enalaprilformulations described herein are useful for the treatment ofhypertension, prehypertension, heart failure as well as ventriculardysfunction. The formulations are advantageous over conventional soliddosage administration of enalapril ranging from ease of administration,accuracy of dosing, accessibility to additional patient populations suchas to children and the elderly, and an increased patient compliance tomedication.

It is generally known that certain segments of the population havedifficulty ingesting and swallowing solid oral dosage forms such astablets and capsules. As many as a quarter of the total population hasthis difficulty. Often, this leads to non-compliance with therecommended medical therapy with the solid dosage forms, therebyresulting in rending the therapy ineffective. Further, solid dosageforms are not recommended for children or elderly due to increased riskin choking.

Furthermore, the dose of enalapril to be given to children is calculatedaccording to the child's weight. When the calculated dose is somethingother than the amount present in one or more intact solid dosage forms,the solid dosage form must be divided to provide the correct dose. Thisleads to inaccurate dosing when solid dosages forms, such as tablets,are compounded to prepare other formulations for children.

For enalapril, one solution to overcoming the use of the tablet form isfor a compounding pharmacist to pulverize and crush the enalapriltablet(s) into a powder via mortar and pestle and reconstitute thepowder in some liquid form. However forming a enalapril oral liquid inthis fashion has significant drawbacks including large variability inthe actual dosage, incomplete solubilizing of the enalapril tablet inthe liquid, rapid instability, inconsistent formulation methods percompounding pharmacy, and a number of other potential issues. Thecrushed tablet liquid formulation may also be potentially unsafe due tocontamination with residual drugs and other substances from the mortarand pestle or other crushing agent.

Alternatively, enalapril is formulated as enalapril powder compositionsfor reconstitution as oral liquids as described in U.S. Pat. No.8,568,747. The powder compositions as described in this patent requiremannitol and colloidal silicon dioxide for stability and dissolution.While these powder compositions are an improvement over crushingtablets, they still require a step of mixing with a diluent. The stableenalapril oral liquid formulations described herein require no extrasteps or manipulation prior to administration to a subject. Further, thestable enalapril oral liquid formulations described herein do notrequire or need mannitol or colloidal silicon dioxide for stability anddissolution.

The present embodiments described herein provide a safe and effectiveoral administration of enalapril for the treatment of hypertension andother disorders. In particular, the embodiments provide stable enalapriloral liquid formulations as well as alternatively enalapril powderformulations for oral liquid administration.

As used herein, “enalapril” refers to enalapril base, its salt, orsolvate or derivative or isomer or polymorph thereof. Suitable compoundsinclude the free base, the organic and inorganic salts, isomers, isomersalts, solvates, polymorphs, complexes etc. U.S. Pat. Nos. 4,374,829;4,472,380 and 4,510,083 disclose exemplary methods in the preparation ofenalapril. In some embodiments, the enalapril used in the formulationsdescribed herein is an enalapril salt. In some instances, the enalaprilsalt is enalapril maleate. In other instances, the enalapril salt is inthe form of enalapril sodium.

Other ACE inhibitors are contemplated in the formulations within andinclude but are not limited to quinapril, indolapril, ramipril,perindopril, lisinopril, benazepril, imidapril, zofenopril,trandolapril, fosinopril, captopril, and their salts, solvates,derivatives, polymorphs, or complexes, thereof.

Enalapril Oral Liquid Formulations

Oral liquids include, but are not limited to, solutions (both aqueousand nonaqueous), suspensions, emulsions, syrups, slurries, juices,elixirs, dispersions, and the like. It is envisioned thatsolution/suspensions are also included where certain componentsdescribed herein are in a solution while other components are in asuspension.

In one aspect, the enalapril liquid formulations described hereincomprise enalapril, a preservative, a sweetening agent, a buffer, andwater. In one embodiment, the sweetening agent is sucralose. In oneembodiment, the sweetening agent is xylitol. In one embodiment, thesweetening agent is not mannitol. In another embodiment, thepreservative is sodium benzoate. In some embodiments, the preservativeis a paraben. In some embodiments, the preservative is a mixture ofparabens. In yet another embodiment, the buffer comprises citric acid.In some embodiments, the buffer further comprises sodium citrate. In oneaspect, the enalapril liquid formulation described herein comprisesenalapril, sucralose, sodium benzoate, citric acid, sodium citrate, andwater. In some embodiments, the enalapril liquid formulation hereinfurther comprises a flavoring agent. In some embodiments, the enalaprilliquid formulation is not obtained from crushing enalapril tablet anddissolving the powder in a suitable vehicle for oral administration. Insome embodiments, the enalapril liquid formulation does not containsilicon dioxide. In some embodiments, the enalapril liquid formulationdoes not contain mannitol. In some embodiments, the enalapril liquidformulation does not contain lactose. In some embodiments, the enalaprilliquid formulation does not contain magnesium stearate. In someembodiments, the enalapril liquid formulation does not contain sodiumbicarbonate. In some embodiments, the enalapril liquid formulation doesnot contain iron oxides.

In some embodiments, enalapril or a pharmaceutically acceptable saltthereof, is present in about 0.6 to about 1.2 mg/ml in the oral liquidformulation. In other embodiments, enalapril or a pharmaceuticallyacceptable salt thereof, is present in about 0.6 mg/ml, about 0.61mg/ml, about 0.62 mg/ml, about 0.63 mg/ml, about 0.64 mg/ml, about 0.65mg/ml, about 0.66 mg/ml, about 0.67 mg/ml, about 0.68 mg/ml, about 0.69mg/ml, about 0.7 mg/ml, about 0.71 mg/ml, about 0.72 mg/ml, about 0.73mg/ml, about 0.74 mg/ml, about 0.75 mg/ml, about 0.76 mg/ml, about 0.77mg/ml, about 0.78 mg/ml, about 0.79 mg/ml, about 0.8 mg/ml, about 0.81mg/ml, about 0.82 mg/ml, about 0.83 mg/ml, about 0.84 mg/ml, about 0.85mg/ml, about 0.86 mg/ml, about 0.87 mg/ml, about 0.88 mg/ml, about 0.89mg/ml, about 0.9 mg/ml, about 0.91 mg/ml, about 0.92 mg/ml, about 0.93mg/ml, about 0.94 mg/ml, about 0.95 mg/ml, about 0.96 mg/ml, about 0.97mg/ml, about 0.98 mg/ml, about 0.99 mg/ml, about 1 mg/ml, about 1.01mg/ml, about 1.02, mg/ml, about 1.03 mg/ml, about 1.04 mg/ml, about 1.05mg/ml, about 1.06 mg/ml, about 1.07 mg/ml, about 1.08 mg/ml, about 1.09mg/ml, about 1.1 mg/ml, about 1.11 mg/ml, about 1.12, mg/ml, about 1.13mg/ml, about 1.14 mg/ml, about 1.15 mg/ml, about 1.16 mg/ml, about 1.17mg/ml, about 1.18 mg/ml, about 1.19 mg/ml, or about 1.2 mg/ml in theliquid oral formulation. In some embodiments, enalapril is present inabout 0.76 mg/ml in the oral liquid formulation. In some embodiments,enalapril maleate is present in about 1 mg/ml in the oral liquidformulation. In some embodiments, the formulation contains enalapril oranother pharmaceutically acceptable salt of enalapril in a molarconcentration equivalent to 1 mg/mL enalapril maleate. In someembodiments, the formulation contains enalapril or anotherpharmaceutically acceptable salt of enalapril in a molar concentrationequivalent to 0.76 mg/mL enalapril.

In some embodiments, enalapril or a pharmaceutically acceptable saltthereof, is present in about 0.5 w/w to about 30% w/w of the solids inthe oral liquid formulation. In other embodiments, enalapril or apharmaceutically acceptable salt thereof, is present in about 0.5 w/w,about 1 w/w, about 1.5% w/w, about 2% w/w, about 2.5 w/w, about 3% w/w,about 3.5 w/w, about 4% w/w, about 4.5% w/w, about 5 w/w, about 5.5 w/w,about 6% w/w, about 6.5 w/w, about 7% w/w, about 7.5% w/w, about 8% w/w,about 8.5 w/w, about 9% w/w, about 9.5 w/w, about 10% w/w, about 10.5%w/w, about 11 w/w, about 11.5 w/w, about 12% w/w, about 12.5 w/w, about13% w/w, about 13.5 w/w, about 14% w/w, about 14.5 w/w, about 15 w/w,about 15.1% w/w, about 15.2% w/w, about 15.3% w/w, about 15.4% w/w,about 15.5 w/w, about 15.6% w/w, about 15.7% w/w, about 15.8% w/w, about15.9% w/w, about 16% w/w, about 16.1% w/w, about 16.2% w/w, about 16.3%w/w, about 16.4% w/w, about 16.5 w/w, about 16.6% w/w, about 16.7% w/w,about 16.8% w/w, about 16.9% w/w, about 17% w/w, about 17.1% w/w, about17.2% w/w, about 17.3% w/w, about 17.4 w/w, about 17.5 w/w, about 17.6%w/w, about 17.7% w/w, about 17.8% w/w, about 17.9% w/w, about 18% w/w,about 18.1% w/w, about 18.2% w/w, about 18.3% w/w, about 18.4% w/w,about 18.5 w/w, about 18.6% w/w, about 18.7% w/w, about 18.8% w/w, about18.9% w/w, about 19% w/w, about 19.1% w/w, about 19.2% w/w, about 19.3%w/w, about 19.4% w/w, about 19.5 w/w, about 19.6% w/w, about 19.7% w/w,about 19.8% w/w, about 19.9% w/w, about 20% w/w, about 20.1% w/w, about20.2% w/w, about 20.3% w/w, about 20.4% w/w, about 20.5 w/w, about 20.6%w/w, about 20.7% w/w, about 20.8% w/w, about 20.9% w/w, about 21% w/w,about 21.1% w/w, about 21.2 w/w, about 21.3% w/w, about 21.4% w/w, about21.5 w/w, about 21.6% w/w, about 21.7% w/w, about 21.8% w/w, about 21.9%w/w, about 22% w/w, about 22.5 w/w, about 23% w/w, about 23.5% w/w,about 24% w/w, about 24.5 w/w, about 25 w/w, about 25.5 w/w, about 26%w/w, about 26.5 w/w, about 27% w/w, about 27.5 w/w, about 28% w/w, about28.5 w/w, about 29% w/w, about 29.5 w/w, or about 30% w/w of the solidsin the oral liquid formulation. In some embodiments, enalapril or apharmaceutically acceptable salt thereof, is present in about 10% w/w toabout 25 w/w of the solids in the oral liquid formulation. In someembodiments, enalapril is present in about 10.5% w/w of the solids inthe oral liquid formulation. In some embodiments, enalapril is presentin about 15% w/w of the solids in the oral liquid formulation. In someembodiments, enalapril is present in about 18.2% w/w of the solids inthe oral liquid formulation. In some embodiments, enalapril maleate ispresent in about 13.5 w/w of the solids in the oral liquid formulation.In some embodiments, enalapril maleate is present in about 19.3% w/w ofthe solids in the oral liquid formulation. In some embodiments,enalapril maleate is present in about 24.5 w/w of the solids in the oralliquid formulation.

In some embodiments, enalapril or a pharmaceutically acceptable saltthereof, is present in about 0.1% w/w to about 1 w/w of the solids inthe oral liquid formulation. In other embodiments, enalapril or apharmaceutically acceptable salt thereof, is present in about 0.1% w/w,about 0.15 w/w, about 0.2% w/w, about 0.25 w/w, about 0.3% w/w, about0.35 w/w, about 0.4% w/w, about 0.45 w/w, about 0.5 w/w, about 0.55 w/w,about 0.6% w/w, about 0.65 w/w, about 0.7% w/w, about 0.75% w/w, about0.8% w/w, about 0.85 w/w, about 0.9% w/w, about 0.95 w/w, or about 1 w/wof the solids in the oral liquid formulation. In some embodiments,enalapril or a pharmaceutically acceptable salt thereof, is present inabout 0.4% w/w to about 0.7% w/w of the solids in the oral liquidformulation. In some embodiments, enalapril is present in about 0.4% w/wof the solids in the oral liquid formulation. In some embodiments,enalapril is present in about 0.5 w/w of the solids in the oral liquidformulation. In some embodiments, enalapril maleate is present in about0.5 w/w of the solids in the oral liquid formulation. In someembodiments, enalapril maleate is present in about 0.6% w/w of thesolids in the oral liquid formulation.

Sweetener in the Enalapril Oral Liquid Formulations

Sweeteners or sweetening agents include any compounds that provide asweet taste. This includes natural and synthetic sugars, natural andartificial sweeteners, natural extracts and any material that initiatesa sweet sensation in a subject. In some embodiments, a solid/powdersweetener is used in the oral liquid formulation described herein. Inother embodiments, a liquid sweetener is used in the oral liquidformulation described herein.

Sugars illustratively include glucose, fructose, sucrose, xylitol,tagatose, sucralose, maltitol, isomaltulose, Isomalt™ (hydrogenatedisomaltulose), lactitol, sorbitol, erythritol, trehalose, maltodextrin,polydextrose, and the like. Other sweeteners illustratively includeglycerin, inulin, erythritol, maltol, acesulfame and salts thereof,e.g., acesulfame potassium, alitame, aspartame, neotame, sodiumcyclamate, saccharin and salts thereof, e.g., saccharin sodium orsaccharin calcium, neohesperidin dihydrochalcone, stevioside, thaumatin,and the like. Sweeteners can be used in the form of crude or refinedproducts such as hydrogenated starch hydrolysates, maltitol syrup, highfructose corn syrup, etc., and as branded products, e.g., Sweet Am™liquid (Product Code 918.003-propylene glycol, ethyl alcohol, andproprietary artificial flavor combination, Flavors of North America) andSweet Am™ powder (Product Code 918.005—maltodextrin, sorbitol, andfructose combination and Product Code 918.010—water, propylene glycol,sorbitol, fructose, and proprietary natural and artificial flavorcombination, Flavors of North America), ProSweet™ (1-10% proprietaryplant/vegetable extract and 90-99% dextrose combination, ViriginiaDare), Maltisweet™ (maltitol solution, Ingredion), Sorbo™ (sorbitol andsorbitol/xylitol solution, SPI Polyols), Invertose™ (high fructose cornsyrup, Ingredion), Rebalance M60 and X60 (sucralose and maltodextrin,Tate and Lyle), and Ora-Sweet® sugar-free flavored syrup (PaddockLaboratories, Inc.). Sweeteners can be used singly or in combinations oftwo or more. Suitable concentrations of different sweeteners can beselected based on published information, manufacturers' data sheets andby routine testing.

In some embodiments, the enalapril oral liquid formulation describedherein comprises a sweetening agent. In some embodiments, the sweeteningagent is sucralose. In some embodiments, the sweetening agent isxylitol. In some embodiments, the sweetener is not mannitol.

In some embodiments, the enalapril oral liquid formulation describedherein comprises sucralose. In some embodiments, sucralose is present inabout 0.5 to about 0.9 mg/ml in the oral liquid formulation. In otherembodiments, sucralose is present in about 0.51 mg/ml, about 0.52 mg/ml,about 0.53 mg/ml, about 0.54 mg/ml, about 0.55 mg/ml, about 0.56 mg/ml,about 0.57 mg/ml, about 0.58 mg/ml, about 0.59 mg/ml, about 0.60 mg/ml,about 0.61 mg/ml, about 0.62 mg/ml, about 0.63 mg/ml, about 0.64 mg/ml,about 0.65 mg/ml, about 0.66 mg/ml, about 0.67 mg/ml, about 0.68 mg/ml,about 0.69 mg/ml, about 0.70 mg/ml, about 0.71 mg/ml, about 0.72 mg/ml,about 0.73 mg/ml, about 0.74 mg/ml, about 0.75 mg/ml, about 0.76 mg/ml,about 0.77 mg/ml, about 0.78 mg/ml, about 0.79 mg/ml, about 0.80 mg/ml,about 0.81 mg/ml, about 0.82 mg/ml, about 0.83 mg/ml, about 0.84 mg/ml,about 0.85 mg/ml, about 0.86 mg/ml, about 0.87 mg/ml, about 0.88 mg/ml,about 0.89 mg/ml, or about 0.90 mg/ml in the oral liquid formulation. Insome embodiments, sucralose is present in about 0.7 mg/ml in the oralliquid formulation.

In some embodiments, sucralose is present in about 1% w/w to about 30%w/w of the solids in the oral liquid formulation. In some embodiments,sucralose is present in about 1% w/w, about 1.5% w/w, about 2% w/w,about 2.5 w/w, about 3% w/w, about 3.5 w/w, about 4% w/w, about 4.5%w/w, about 5 w/w, about 5.5 w/w, about 6% w/w, about 6.5 w/w, about 7%w/w, about 7.5% w/w, about 8% w/w, about 8.5 w/w, about 9% w/w, about9.5 w/w, about 10% w/w, about 10.5% w/w, about 11 w/w, about 11.5 w/w,about 12% w/w, about 12.5 w/w, about 13% w/w, about 13.5 w/w, about 14%w/w, about 14.5 w/w, about 15 w/w, about 15.5 w/w, about 16% w/w, about16.5 w/w, about 17% w/w, about 17.5 w/w, about 18% w/w, about 18.5 w/w,about 19% w/w, about 19.5 w/w, about 20% w/w, about 20.5 w/w, about 21%w/w, about 21.5 w/w, about 22% w/w, about 22.5 w/w, about 23% w/w, about23.5 w/w, about 24% w/w, about 24.5 w/w, about 25 w/w, about 25.5 w/w,about 26% w/w, about 26.5 w/w, about 27% w/w, about 27.5% w/w, about 28%w/w, about 28.5 w/w, about 29% w/w, about 29.5 w/w, or about 30% w/w ofthe solids in the oral liquid formulation. In some embodiments,sucralose is present in about 8% w/w to about 18% w/w of the solids inthe oral liquid formulation. In some embodiments, sucralose is presentin about 9.5% w/w of the solids in the oral liquid formulation. In someembodiments, sucralose is present in about 13.5% w/w of the solids inthe oral liquid formulation. In some embodiments, sucralose is presentin about 16.5% w/w of the solids in the oral liquid formulation.

In some embodiments, the enalapril oral liquid formulation describedherein comprises xylitol. In some embodiments, xylitol is present inabout 140 mg/ml to about 210 mg/ml in the oral liquid formulation.

In some embodiments, xylitol is present in about 140 mg/ml, about 145mg/ml, about 150 mg/ml, about 155 mg/ml, about 160 mg/ml, about 165mg/ml, about 170 mg/ml, about 175 mg/ml, about 180 mg/ml, about 185mg/ml, about 190 mg/ml, about 195 mg/ml, about 200 mg/ml, about 205mg/ml, or about 210 mg/ml of the oral liquid formulation. In someembodiments, xylitol is present in about 150 mg/ml in the oral liquidformulation. In some embodiments, xylitol is present in about 200 mg/mlin the oral liquid formulation.

In some embodiments, xylitol is present in about 80% w/w to about 99%w/w of the solids in the oral liquid formulation. In other embodiments,xylitol is present in about 80% w/w, about 81% w/w, about 82% w/w, about83% w/w, about 84% w/w, about 85% w/w, about 86% w/w, about 87% w/w,about 88% w/w, about 89% w/w, about 90% w/w, about 91% w/w, about 92%w/w, about 93% w/w, about 94% w/w, about 95% w/w, about 96% w/w, about97% w/w, about 98% w/w, or about 99% w/w of the solids in the oralliquid formulation. In some embodiments, xylitol is present in about 96%w/w to about 98% w/w of the solids in the oral liquid formulation. Insome embodiments, xylitol is present in about 96% w/w of the solids inthe oral liquid formulation.

Preservative in the Enalapril Oral Liquid Formulations

Preservatives include anti-microbials, anti-oxidants, and agents thatenhance sterility. Exemplary preservatives include ascorbic acid,ascorbyl palmitate, BHA, BHT, citric acid, EDTA and its salts,erythorbic acid, fumaric acid, malic acid, propyl gallate, sodiumascorbate, sodium bisulfate, sodium metabisulfite, sodium sulfite,parabens (such as methylparaben, ethylparaben, propylparaben,butylparaben and their salts), benzoic acid, sodium benzoate, potassiumsorbate, vanillin, and the like.

In some embodiments, the enalapril oral liquid formulation describedherein comprises a preservative.

In some embodiments, the preservative is a paraben and the sweetener isnot a sugar (such as, but not limited to glucose, fructose, sucrose,lactose, maltose) or a sugar alcohol (such as, but not limited toxylitol, mannitol, lactitol, maltitol, sorbitol).

In some embodiments, the preservative is sodium benzoate.

In some embodiments, modulation of the pH is desired to provide the bestantimicrobial activity of the preservative, sodium benzoate. In someembodiments, the antimicrobial activity of sodium benzoate drops whenthe pH is increased above 5.

In some embodiments, the pH of the enalapril oral liquid formulationdescribed herein is less than about 4. In some embodiments, the pH ofthe enalapril oral liquid formulation described herein is less thanabout 3.5. In some embodiments, the pH of the enalapril oral liquidformulation described herein is between about 3 and about 4. In someembodiments, the pH of the enalapril oral liquid formulation describedherein is between about 3 and about 3.5. In some embodiments, the pH ofthe enalapril oral liquid formulation described herein is about 3, about3.1, about 3.2, about 3.3, about 3.4, about 3.5, about 3.6, about 3.7,about 3.8, about 3.9, or about 4. In some embodiments, the pH of theenalapril oral liquid formulation described herein is about 3.3.

In some embodiments, sodium benzoate is present in about 0.2 to about1.2 mg/ml in the oral liquid formulation. In other embodiments, sodiumbenzoate is present in about 0.2 mg/ml, about 0.21 mg/ml, about 0.22mg/ml, about 0.23 mg/ml, about 0.24 mg/ml, about 0.25 mg/ml, about 0.26mg/ml, about 0.27 mg/ml, about 0.28 mg/ml, about 0.29 mg/ml, about 0.3mg/ml, about 0.31 mg/ml, about 0.32 mg/ml, about 0.33 mg/ml, about 0.34mg/ml, about 0.35 mg/ml, about 0.36 mg/ml, about 0.37 mg/ml, about 0.38mg/ml, about 0.39 mg/ml, about 0.4 mg/ml, about 0.41 mg/ml, about 0.42mg/ml, about 0.43 mg/ml, about 0.44 mg/ml, about 0.45 mg/ml, about 0.46mg/ml, about 0.47 mg/ml, about 0.48 mg/ml, about 0.49 mg/ml, about 0.5mg/ml, about 0.51 mg/ml, about 0.52 mg/ml, about 0.53 mg/ml, about 0.54mg/ml, about 0.55 mg/ml, about 0.56 mg/ml, about 0.57 mg/ml, about 0.58mg/ml, about 0.59 mg/ml, about 0.6 mg/ml, about 0.61 mg/ml, about 0.62mg/ml, about 0.63 mg/ml, about 0.64 mg/ml, about 0.65 mg/ml, about 0.66mg/ml, about 0.67 mg/ml, about 0.68 mg/ml, about 0.69 mg/ml, about 0.7mg/ml, about 0.71 mg/ml, about 0.72 mg/ml, about 0.73 mg/ml, about 0.74mg/ml, about 0.75 mg/ml, about 0.76 mg/ml, about 0.77 mg/ml, about 0.78mg/ml, about 0.79 mg/ml, about 0.8 mg/ml, about 0.81 mg/ml, about 0.82mg/ml, about 0.83 mg/ml, about 0.84 mg/ml, about 0.85 mg/ml, about 0.86mg/ml, about 0.87 mg/ml, about 0.88 mg/ml, about 0.89 mg/ml, about 0.9mg/ml, about 0.91 mg/ml, about 0.92 mg/ml, about 0.93 mg/ml, about 0.94mg/ml, about 0.95 mg/ml, about 0.96 mg/ml, about 0.97 mg/ml, about 0.98mg/ml, about 0.99 mg/ml, about 1 mg/ml, about 1.01 mg/ml, about 1.02,mg/ml, about 1.03 mg/ml, about 1.04 mg/ml, about 1.05 mg/ml, about 1.06mg/ml, about 1.07 mg/ml, about 1.08 mg/ml, about 1.09 mg/ml, about 1.1mg/ml, about 1.11 mg/ml, about 1.12, mg/ml, about 1.13 mg/ml, about 1.14mg/ml, about 1.15 mg/ml, about 1.16 mg/ml, about 1.17 mg/ml, about 1.18mg/ml, about 1.19 mg/ml, or about 1.2 mg/ml in the liquid oralformulation. In some embodiments, sodium benzoate is present in about 1mg/ml in the oral liquid formulation.

In some embodiments, sodium benzoate is present in about 1% w/w to about30% w/w of the solids in the oral liquid formulation. In otherembodiments, sodium benzoate is present in about 1% w/w, about 1.5 w/w,about 2% w/w, about 2.5 w/w, about 3% w/w, about 3.5 w/w, about 4% w/w,about 4.5 w/w, about 5 w/w, about 5.5 w/w, about 6% w/w, about 6.5 w/w,about 7% w/w, about 7.5 w/w, about 8% w/w, about 8.5 w/w, about 9% w/w,about 9.5 w/w, about 10% w/w, about 10.5 w/w, about 11 w/w, about 11.5w/w, about 12% w/w, about 12.5 w/w, about 13% w/w, about 13.5 w/w, about14% w/w, about 14.5 w/w, about 15 w/w, about 15.1% w/w, about 15.2% w/w,about 15.3% w/w, about 15.4% w/w, about 15.5 w/w, about 15.6% w/w, about15.7% w/w, about 15.8% w/w, about 15.9% w/w, about 16% w/w, about 16.1%w/w, about 16.2% w/w, about 16.3% w/w, about 16.4% w/w, about 16.5 w/w,about 16.6% w/w, about 16.7% w/w, about 16.8% w/w, about 16.9% w/w,about 17% w/w, about 17.1% w/w, about 17.2% w/w, about 17.3% w/w, about17.4% w/w, about 17.5 w/w, about 17.6% w/w, about 17.7% w/w, about 17.8%w/w, about 17.9% w/w, about 18% w/w, about 18.1% w/w, about 18.2% w/w,about 18.3% w/w, about 18.4 w/w, about 18.5 w/w, about 18.6% w/w, about18.7% w/w, about 18.8% w/w, about 18.9% w/w, about 19% w/w, about 19.1%w/w, about 19.2% w/w, about 19.3% w/w, about 19.4% w/w, about 19.5% w/w,about 19.6% w/w, about 19.7% w/w, about 19.8% w/w, about 19.9% w/w,about 20% w/w, about 20.1% w/w, about 20.2% w/w, about 20.3% w/w, about20.4% w/w, about 20.5 w/w, about 20.6% w/w, about 20.7% w/w, about 20.8%w/w, about 20.9% w/w, about 21% w/w, about 21.1% w/w, about 21.2% w/w,about 21.3% w/w, about 21.4% w/w, about 21.5 w/w, about 21.6% w/w, about21.7% w/w, about 21.8% w/w, about 21.9% w/w, about 22% w/w, about 22.5w/w, about 23% w/w, about 23.5 w/w, about 24% w/w, about 24.5 w/w, about25 w/w, about 25.5 w/w, about 26% w/w, about 26.5 w/w, about 27% w/w,about 27.5 w/w, about 28% w/w, about 28.5% w/w, about 29% w/w, about29.5 w/w, or about 30% w/w of the solids in the oral liquid formulation.In some embodiments, sodium benzoate is present in about 10% w/w toabout 25 w/w of the solids in the oral liquid formulation. In someembodiments, sodium benzoate is present in about 13.5% w/w of the solidsin the oral liquid formulation. In some embodiments, sodium benzoate ispresent in about 19.3% w/w of the solids in the oral liquid formulation.In some embodiments, sodium benzoate is present in about 23.5% w/w ofthe solids in the oral liquid formulation.

In some embodiments, sodium benzoate is present in about 0.1% w/w toabout 1 w/w of the solids in the oral liquid formulation. In otherembodiments, sodium benzoate is present in about 0.1% w/w, about 0.15w/w, about 0.2% w/w, about 0.25 w/w, about 0.3% w/w, about 0.35 w/w,about 0.4% w/w, about 0.45 w/w, about 0.5 w/w, about 0.55 w/w, about0.6% w/w, about 0.65 w/w, about 0.7% w/w, about 0.75 w/w, about 0.8%w/w, about 0.85 w/w, about 0.9% w/w, about 0.95% w/w, or about 1 w/w ofthe solids in the oral liquid formulation. In some embodiments, sodiumbenzoate is present in about 0.4% w/w to about 0.7% w/w of the solids inthe oral liquid formulation. In some embodiments, sodium benzoate ispresent in about 0.45% w/w of the solids in the oral liquid formulation.In some embodiments, sodium benzoate is present in about 0.6% w/w of thesolids in the oral liquid formulation.

In some embodiments, sodium benzoate is present in an amount sufficientto provide antimicrobial effectiveness to the enalapril oral liquidformulation described herein. (See Table G-1).

In some embodiments, the preservative is a paraben. In some embodiments,the preservative is a mixture of parabens. In some embodiments, theparaben or mixture of parabens is present in about 0.1 mg/ml to about 2mg/ml in the oral liquid formulation. In other embodiments, the parabenor mixture of parabens is present in about 0.1 mg/ml, about 0.2 mg/ml,about 0.3 mg/ml, about 0.4 mg/ml, about 0.5 mg/ml, about 0.6 mg/ml,about 0.7 mg/ml, about 0.8 mg/ml, about 0.9 mg/ml, about 1 mg/ml, about1.1 mg/ml, about 1.2 mg/ml, about 1.3 mg/ml, about 1.4 mg/ml, or about1.5 mg/ml, about 1.6 mg/ml, about 1.7 mg/ml, about 1.8 mg/ml, about 1.9mg/ml, or about 2 mg/ml in the liquid oral formulation. In someembodiments, the paraben or mixture of parabens is present in about 1.6mg/ml to about 2 mg/ml in the oral liquid formulation. In someembodiments, the paraben or mixture of parabens is present in about 1.6mg/ml to about 1.8 mg/ml in the oral liquid formulation. In someembodiments, the paraben or mixture of parabens is present in about 0.1mg/ml to about 0.5 mg/ml in the oral liquid formulation.

In some embodiments, the paraben or mixture of parabens is present inabout 2% w/w to about 30% w/w of the solids in the oral liquidformulation. In other embodiments, the paraben or mixture of parabens ispresent in about 2% w/w, about 3% w/w, about 4% w/w, about 5% w/w, about6% w/w, about 7% w/w, about 8% w/w, about 9% w/w, about 10% w/w, about11% w/w, about 12% w/w, about 13% w/w, about 14% w/w, about 15% w/w,about 16% w/w, about 17% w/w, about 18% w/w, about 19% w/w, about 20%w/w, about 21% w/w, about 22% w/w, about 23% w/w, about 24% w/w, about25% w/w, about 26% w/w, about 27% w/w, about 28% w/w, about 29% w/w, orabout 30% w/w of the solids in the oral liquid formulation. In someembodiments, the paraben or mixture of parabens is present in about 2%w/w to about 3% w/w of the solids in the oral liquid formulation. Insome embodiments, the paraben or mixture of parabens is present in about23% w/w to about 26% w/w of the solids in the oral liquid formulation.In some embodiments, the paraben or mixture of parabens is present inabout 26% w/w to about 30% w/w of the solids in the oral liquidformulation.

Sweetener and Preservative Incompatibility

Paraben preservatives (especially methylparaben) can react with selectedsugars (glucose, fructose, sucrose, lactose, maltose) and sugar alcohols(xylitol, mannitol, lactitol, maltitol, sorbitol) to formtransesterification reaction products. This can be undesirable from aformulation and stability standpoint as the transesterification createsadditional degradants.

In some embodiments, the enalapril oral liquid formulation describedherein does not comprise a paraben preservative. In further embodiments,the enalapril oral liquid formulation described herein does not comprisea paraben preservative when the formulation also comprises a sugar orsugar alcohol.

pH of Enalapril Oral Liquid Formulations

Buffering agents maintain the pH of the liquid enalapril formulation.Non-limiting examples of buffering agents include, but are not limitedto sodium bicarbonate, potassium bicarbonate, magnesium hydroxide,magnesium lactate, magnesium glucomate, aluminum hydroxide, aluminumhydroxide/sodium bicarbonate co-precipitate, mixture of an amino acidand a buffer, a mixture of aluminum glycinate and a buffer, a mixture ofan acid salt of an amino acid and a buffer, and a mixture of an alkalisalt of an amino acid and a buffer. Additional buffering agents includecitric acid, sodium citrate, sodium tartarate, sodium acetate, sodiumcarbonate, sodium polyphosphate, potassium polyphosphate, sodiumpyrophosphate, potassium pyrophosphate, disodium hydrogenphosphate,dipotassium hydrogenphosphate, trisodium phosphate, tripotassiumphosphate, sodium acetate, potassium metaphosphate, magnesium oxide,magnesium hydroxide, magnesium carbonate, magnesium silicate, calciumacetate, calcium glycerophosphate, calcium chloride, calcium hydroxide,calcium lactate, calcium carbonate, calcium bicarbonate, and othercalcium salts. Some buffering agents also impart effervescent qualitieswhen a powder is reconstituted in a solution. In some embodiments, thebuffering agent is not sodium bicarbonate.

In some embodiments, the oral liquid formulation comprises a buffer.

In some embodiments, the buffer in the enalapril oral liquid formulationdescribed herein comprises citric acid. In some embodiments, the bufferin the enalapril oral liquid formulation described herein comprisescitric acid and sodium citrate. In some embodiments, the buffer in theenalapril oral liquid formulation described herein comprises citric acidand sodium citrate dihydrate or an equivalent molar amount of sodiumcitrate anhydrous. In some embodiments, the sodium citrate is monosodiumCitrate. In some embodiments, the sodium citrate is disodium citrate. Insome embodiments, the sodium citrate is trisodium citrate.

In some embodiments, the buffer in the enalapril oral liquid formulationdescribed herein comprises phosphoric acid. In some embodiments, thebuffer in the enalapril oral liquid formulation described hereincomprises sodium phosphate.

In some embodiments, modulation of the pH is desired to provide alowered impurity profile. In the exemplary stability studies, the mainenalapril degradants are enalapril diketopiperazine and enalaprilat:

In some embodiments, the percentage of enalaprilat formation isincreased when the pH is above 3.5. (See table C-2 and FIG. 1 and FIG.2). In some embodiments, the percentage of enalapril diketopiperazineformation is slightly increased as the pH is below 4.

In some embodiments, the pH of the enalapril oral liquid formulationdescribed herein is less than about 4. In some embodiments, the pH ofthe enalapril oral liquid formulation described herein is less thanabout 3.5. In some embodiments, the pH of the enalapril oral liquidformulation described herein is between about 3 and about 4. In someembodiments, the pH of the enalapril oral liquid formulation describedherein is between about 3 and about 3.5. In some embodiments, the pH ofthe enalapril oral liquid formulation described herein is about 3, about3.1, about 3.2, about 3.3, about 3.4, about 3.5, about 3.6, about 3.7,about 3.8, about 3.9, or about 4. In some embodiments, the pH of theenalapril oral liquid formulation described herein is about 3.3.

In some embodiments, the formation of degradants is dependent on thebuffer concentration. In some embodiments, the buffer concentrationimpacts the taste of the enalapril oral liquid formulation.

In some embodiments, the buffer concentration is between about 5 mM andabout 20 mM. In some embodiments, the buffer concentration is about 5mM, about 6 mM, about 7 mM, about 8 mM, about 9 mM, about 10 mM, about11 mM, about 12 mM, about 13 mM, about 14 mM, about 15 mM, about 16 mM,about 17 mM, about 18 mM, about 19 mM, or about 20 mM. In someembodiments, the buffer concentration is about 5 mM. In someembodiments, the buffer concentration is about 10 mM. In someembodiments, the buffer concentration is about 20 mM.

In some embodiments, citric acid is present in about 0.7 to about 2mg/ml in the oral liquid formulation. In other embodiments, citric acidis present in about 0.7 mg/ml, about 0.71 mg/ml, about 0.72 mg/ml, about0.73 mg/ml, about 0.74 mg/ml, about 0.75 mg/ml, about 0.76 mg/ml, about0.77 mg/ml, about 0.78 mg/ml, about 0.79 mg/ml, about 0.8 mg/ml, about0.81 mg/ml, about 0.82 mg/ml, about 0.83 mg/ml, about 0.84 mg/ml, about0.85 mg/ml, about 0.86 mg/ml, about 0.87 mg/ml, about 0.88 mg/ml, about0.89 mg/ml, about 0.9 mg/mL, about 0.91 mg/mL, about 0.92 mg/mL, about0.93 mg/mL, about 0.94 mg/mL, about 0.95 mg/mL, about 0.96 mg/mL, about0.97 mg/mL, about 0.98 mg/mL, about 0.99 mg/mL, about 1 mg/mL, about1.11 mg/ml, about 1.12 mg/ml, about 1.13 mg/ml, about 1.14 mg/ml, about1.15 mg/ml, about 1.16 mg/ml, about 1.17 mg/ml, about 1.18 mg/ml, about1.19 mg/ml, about 1.2 mg/ml, about 1.21 mg/ml, about 1.22 mg/ml, about1.23 mg/ml, about 1.24 mg/ml, about 1.25 mg/ml, about 1.26 mg/ml, about1.27 mg/ml, about 1.28 mg/ml, about 1.29 mg/ml, about 1.3 mg/mL, about1.31 mg/mL, about 1.32 mg/mL, about 1.33 mg/mL, about 1.34 mg/mL, about1.35 mg/mL, about 1.36 mg/mL, about 1.37 mg/mL, about 1.38 mg/mL, about1.39 mg/mL, about 1.4 mg/ml, about 1.41 mg/ml, about 1.42 mg/ml, about1.43 mg/ml, about 1.44 mg/ml, about 1.45 mg/ml, about 1.46 mg/ml, about1.47 mg/ml, about 1.48 mg/ml, about 1.49 mg/ml, about 1.5 mg/ml, about1.51 mg/ml, about 1.52 mg/ml, about 1.53 mg/ml, about 1.54 mg/ml, about1.55 mg/ml, about 1.56 mg/ml, about 1.57 mg/ml, about 1.58 mg/ml, about1.59 mg/ml, about 1.6 mg/mL, about 1.61 mg/mL, about 1.62 mg/mL, about1.63 mg/mL, about 1.64 mg/mL, about 1.65 mg/mL, about 1.66 mg/mL, about1.67 mg/mL, about 1.68 mg/mL, about 1.69 mg/mL, about 1.7 mg/ml, about1.71 mg/ml, about 1.72 mg/ml, about 1.73 mg/ml, about 1.74 mg/ml, about1.75 mg/ml, about 1.76 mg/ml, about 1.77 mg/ml, about 1.78 mg/ml, about1.79 mg/ml, about 1.8 mg/ml, about 1.81 mg/ml, about 1.82 mg/ml, about1.83 mg/ml, about 1.84 mg/ml, about 1.85 mg/ml, about 1.86 mg/ml, about1.87 mg/ml, about 1.88 mg/ml, about 1.89 mg/ml, about 1.9 mg/mL, about1.91 mg/mL, about 1.92 mg/mL, about 1.93 mg/mL, about 1.94 mg/mL, about1.95 mg/mL, about 1.96 mg/mL, about 1.97 mg/mL, about 1.98 mg/mL, about1.99 mg/mL, or about 2 mg/mL in the oral liquid formulation. In someembodiments, citric acid is present in about 1.65 mg/ml in the oralliquid formulation. In some embodiments, citric acid is present in about1.82 mg/ml in the oral liquid formulation. In some embodiments, citricacid is present in about 0.82 mg/ml in the oral liquid formulation.

In some embodiments, citric acid is present in about 2 to about 3.5mg/ml in the oral liquid formulation. In other embodiments, citric acidis present in about 2 mg/mL, about 2.05 mg/mL, about 2.1 mg/mL, about2.15 mg/mL, about 2.2 mg/mL, about 2.25 mg/mL, about 2.3 mg/mL, about2.35 mg/mL, about 2.4 mg/mL, about 2.45 mg/mL, about 2.5 mg/mL, about2.55 mg/mL, about 2.6 mg/mL, about 2.65 mg/mL, about 2.7 mg/mL, about2.75 mg/mL, about 2.8 mg/mL, about 2.85 mg/mL, about 2.9 mg/mL, about2.95 mg/mL, about 3 mg/mL, about 3.05 mg/ml, about 3.1 mg/mL, about 3.15mg/mL, about 3.2 mg/mL, about 3.25 mg/mL, about 3.3 mg/mL, about 3.35mg/mL, about 3.4 mg/mL, about 3.45 mg/mL, or about 3.5 mg/mL in the oralliquid formulation. In some embodiments, citric acid is present in about3.3 mg/ml in the oral liquid formulation.

In some embodiments, citric acid is present in about 10% w/w to about 50w/w of the solids in the oral liquid formulation. In other embodiments,citric acid is present in about 10% w/w, about 11% w/w, about 12% w/w,about 13% w/w, about 14% w/w, about 15 w/w, about 16% w/w, about 17%w/w, about 18% w/w, about 19% w/w, about 20% w/w, about 21% w/w, about22% w/w, about 23% w/w, about 24% w/w, about 25 w/w, about 26% w/w,about 27% w/w, about 28% w/w, about 29% w/w, about 30% w/w, about 31%w/w, about 32% w/w, about 33% w/w, about 34% w/w, about 35% w/w, about36% w/w, about 37% w/w, about 38% w/w, about 39% w/w, about 40% w/w,about 41% w/w, about 42% w/w, about 43% w/w, about 44% w/w, about 45w/w, about 46% w/w, about 47% w/w, about 48% w/w, about 49% w/w, about50% w/w of the solids in the oral liquid formulation. In someembodiments, citric acid is present in about 45 w/w of the solids in theoral liquid formulation. In some embodiments, citric acid is present inabout 31% w/w of the solids in the oral liquid formulation. In someembodiments, citric acid is present in about 35 w/w of the solids in theoral liquid formulation. In some embodiments, citric acid is present inabout 19% w/w of the solids in the oral liquid formulation.

In some embodiments, citric acid is present in about 1 w/w to about 5w/w of the solids in the oral liquid formulation. In other embodiments,citric acid is present in about 1% w/w, about 1.1% w/w, about 1.2% w/w,about 1.3% w/w, about 1.4% w/w, about 1.5 w/w, about 1.6% w/w, about1.7% w/w, about 1.8% w/w, about 1.9% w/w, about 2% w/w, about 2.1% w/w,about 2.2% w/w, about 2.3% w/w, about 2.4% w/w, about 2.5 w/w, about2.6% w/w, about 2.7% w/w, about 2.8% w/w, about 2.9% w/w, about 3% w/w,about 3.1% w/w, about 3.2% w/w, about 3.3% w/w, about 3.4% w/w, about3.5 w/w, about 3.6% w/w, about 3.7% w/w, about 3.8% w/w, about 3.9% w/w,about 4% w/w, about 4.1% w/w, about 4.2% w/w, about 4.3% w/w, about 4.4%w/w, about 4.5 w/w, about 4.6% w/w, about 4.7% w/w, about 4.8% w/w,about 4.9% w/w, or about 5 w/w of the solids in the oral liquidformulation. In some embodiments, citric acid is present in about 2.1%w/w of the solids in the oral liquid formulation. In some embodiments,citric acid is present in about 1.6% w/w of the solids in the oralliquid formulation.

In some embodiments, sodium citrate dihydrate is present in about 0.1 toabout 0.8 mg/ml in the oral liquid formulation. In other embodiments,sodium citrate dihydrate is present in the oral liquid formulation isabout 0.1 mg/mL, about 0.11 mg/mL, about 0.12 mg/mL, about 0.13 mg/mL,about 0.14 mg/mL, about 0.15 mg/ml, about 0.16 mg/mL, about 0.17 mg/mL,about 0.18 mg/mL, about 0.19 mg/mL, about 0.2 mg/ml, about 0.21 mg/ml,about 0.22 mg/ml, about 0.23 mg/ml, about 0.24 mg/ml, about 0.25 mg/ml,about 0.26 mg/ml, about 0.27 mg/ml, about 0.28 mg/ml, about 0.29 mg/ml,about 0.3 mg/ml, about 0.31 mg/ml, about 0.32 mg/ml, about 0.33 mg/ml,about 0.34 mg/ml, about 0.35 mg/ml, about 0.36 mg/ml, about 0.37 mg/ml,about 0.38 mg/ml, about 0.39 mg/ml, about 0.4 mg/ml, about 0.41 mg/ml, about 0.42 mg/ml, about 0.43 mg/ml, about 0.44 mg/ml, about 0.45 mg/ml,about 0.46 mg/ml, about 0.47 mg/ml, about 0.48 mg/ml, about 0.49 mg/ml,about 0.5 mg/ml, about 0.51 mg/ml, about 0.52 mg/ml, about 0.53 mg/ml,about 0.54 mg/ml, about 0.55 mg/ml, about 0.56 mg/ml, about 0.57 mg/ml,about 0.58 mg/ml, about 0.59 mg/ml, about 0.6 mg/ml, about 0.61 mg/ml,about 0.62 mg/ml, about 0.63 mg/ml, about 0.64 mg/ml, about 0.65 mg/ml,about 0.66 mg/ml, about 0.67 mg/ml, about 0.68 mg/ml, about 0.69 mg/ml,about 0.7 mg/ml, about 0.71 mg/ml, about 0.72 mg/ml, about 0.73 mg/ml,about 0.74 mg/ml, about 0.75 mg/ml, about 0.76 mg/ml, about 0.77 mg/ml,about 0.78 mg/ml, about 0.79 mg/ml, or about 0.8 mg/ml in the oralliquid formulation. In some embodiments, sodium citrate dihydrate ispresent in about 0.75 mg/ml in the oral liquid formulation. In someembodiments, sodium citrate dihydrate is present in about 0.35 mg/ml inthe oral liquid formulation. In some embodiments, sodium citratedihydrate is present in about 0.2 mg/ml in the oral liquid formulation.In some embodiments, sodium citrate dihydrate is present in about 0.15mg/ml in the oral liquid formulation.

In some embodiments, sodium citrate dihydrate is present in about 1 w/wto about 15% w/w of the solids in the oral liquid formulation. In otherembodiments, sodium citrate dihydrate is present in about 1 w/w, about1.1% w/w, about 1.2% w/w, about 1.3% w/w, about 1.4% w/w, about 1.5%w/w, about 1.6% w/w, about 1.7% w/w, about 1.8% w/w, about 1.9% w/w,about 2% w/w, about 2.1% w/w, about 2.2% w/w, about 2.3% w/w, about 2.4%w/w, about 2.5 w/w, about 2.6% w/w, about 2.7% w/w, about 2.8% w/w,about 2.9% w/w, about 3% w/w, about 3.1% w/w, about 3.2% w/w, about 3.3%w/w, about 3.4% w/w, about 3.5 w/w, about 3.6% w/w, about 3.7% w/w,about 3.8% w/w, about 3.9% w/w, about 4% w/w, about 4.5 w/w, about 5w/w, about 5.5 w/w, about 6% w/w, about 6.5 w/w, about 7% w/w, about 7.5w/w, about 8% w/w, about 8.5 w/w, about 9% w/w, about 9.5 w/w, about 10%w/w, about 10.5 w/w, about 11 w/w, about 11.5 w/w, about 12% w/w, about12.5 w/w, about 13% w/w, about 13.5 w/w, about 14% w/w, about 14.5 w/w,about 15 w/w of the solids in the oral liquid formulation. In someembodiments, sodium citrate dihydrate is present in about 10.5 w/w ofthe solids in the oral liquid formulation. In some embodiments, sodiumcitrate dihydrate is present in about 7.5 w/w of the solids in the oralliquid formulation. In some embodiments, sodium citrate dihydrate ispresent in about 4.5 w/w of the solids in the oral liquid formulation.In some embodiments, sodium citrate dihydrate is present in about 2.9%w/w of the solids in the oral liquid formulation.

In other embodiments, sodium citrate dihydrate is not added to theformulation.

Additional Excipients

In further embodiments, the enalapril liquid formulation describedherein comprises additional excipients including, but not limited to,glidants, flavoring agents, coloring agents and thickeners. Additionalexcipients such as bulking agents, tonicity agents and chelating agentsare within the scope of the embodiments.

Glidants are substances that improve flowability of a powder. Suitableglidants include, but are not limited to, calcium phosphate tribasic,calcium silicate, cellulose (powdered), colloidal silicon dioxide,magnesium silicate, magnesium trisilicate, silicon dioxide, starch, talcand the like. In some embodiments, the enalapril powder formulationsdescribed herein comprise a glidant. In some embodiments the glidant isnot colloidal silicon dioxide.

In another embodiment, the enalapril liquid formulation comprises aflavoring agent or flavorant to enhance the taste or aroma of theformulation in liquid form. Suitable natural or synthetic flavoringagents can be selected from standard reference books, for exampleFenaroli's Handbook of Flavor Ingredients, 3rd edition (1995).Non-limiting examples of suitable natural flavors, some of which canreadily be simulated with synthetic agents or combinations thereof,include almond, anise, apple, apricot, bergamot, blackberry,blackcurrant, blueberry, cacao, caramel, cherry, cinnamon, clove,coffee, coriander, cranberry, cumin, dill, eucalyptus, fennel, fig,ginger, grape, grapefruit, guava, hop, lemon, licorice, lime, malt,mandarin, molasses, nutmeg, mixed berry, orange, peach, pear,peppermint, pineapple, raspberry, rose, spearmint, strawberry,tangerine, tea, vanilla, wintergreen, etc. Also useful, particularlywhere the formulation is intended primarily for pediatric use, istutti-frutti or bubblegum flavor, a compounded flavoring agent based onfruit flavors. Presently preferred flavoring agents include anise,cinnamon, cacao, orange, peppermint, cherry (in particular wild cherry),grape, bubblegum, vanilla, and mixed berry. In some embodiments, theenalapril liquid formulation described herein comprises a mixed berryflavoring agent. Flavoring agents can be used singly or in combinationsof two or more.

In further embodiments, the enalapril liquid formulation comprises acoloring agent for identity and/or aesthetic purposes. Suitable coloringagents illustratively include FD&C Red No. 3, FD&C Red No. 20, FD&C RedNo. 40, FD&C Yellow No. 6, FD&C Blue No. 2, FD&C Green No. 5, FD&COrange No. 5, caramel, ferric oxide and mixtures thereof.

Thickeners impart viscosity or weight to the resultant liquid forms fromthe enalapril formulation described herein. Exemplary thickeners includedextrin, cellulose derivatives (carboxymethylcellulose and its salts,ethylcellulose, hydroxyethyl cellulose, methylcellulose, hypromellose,and the like) starches, pectin, polyethylene glycol, polyethylene oxide,trehalose and certain gums (xanthan gum, locust bean gum, etc.). Incertain embodiments, the enalapril liquid formulation comprises athickener.

Additional excipients are contemplated in the enalapril liquidformulation embodiments. These additional excipients are selected basedon function and compatibility with the enalapril liquid formulationsdescribed herein and may be found, for example in Remington: The Scienceand Practice of Pharmacy, Nineteenth Ed (Easton, Pa.: Mack PublishingCompany, 1995); Hoover, John E., Remington's Pharmaceutical Sciences,(Easton, Pa.: Mack Publishing Co 1975); Liberman, H. A. and Lachman, L.,Eds., Pharmaceutical Dosage Forms (New York, N.Y.: Marcel Decker 1980);and Pharmaceutical Dosage Forms and Drug Delivery Systems, Seventh Ed(Lippincott Williams & Wilkins 1999), herein incorporated by referencein their entirety.

Stability

The main enalapril degradants are enalapril diketopiperazine andenalaprilat.

The enalapril oral liquid formulations described herein are stable invarious storage conditions including refrigerated, ambient andaccelerated conditions. Stable as used herein refers to enalapril oralliquid formulations having about 95% or greater of the initial enalaprilamount and about 5% w/w or less total impurities or related substancesat the end of a given storage period. The percentage of impurities iscalculated from the amount of impurities relative to the amount ofenalapril. Stability is assessed by HPLC or any other known testingmethod. In some embodiments, the stable enalapril oral liquidformulations have about 5% w/w, about 4% w/w, about 3% w/w, about 2.5%w/w, about 2% w/w, about 1.5% w/w, about 1% w/w, or about 0.5% w/w totalimpurities or related substances. In other embodiments, the stableenalapril oral liquid formulations have about 5% w/w total impurities orrelated substances. In yet other embodiments, the stable enalapril oralliquid formulations have about 4% w/w total impurities or relatedsubstances. In yet other embodiments, the stable enalapril oral liquidformulations have about 3% w/w total impurities or related substances.In yet other embodiments, the stable enalapril oral liquid formulationshave about 2% w/w total impurities or related substances. In yet otherembodiments, the stable enalapril oral liquid formulations have about 1%w/w total impurities or related substances.

At refrigerated condition, the enalapril oral liquid formulationsdescribed herein are stable for at least 1 month, at least 2 months, atleast 3 months, at least 6 months, at least 9 months, at least 12months, at least 15 months, at least 18 months, at least 24 months, atleast 30 months and at least 36 months. In some embodiments,refrigerated condition is 5±3° C. In some embodiments, refrigeratedcondition is about 2° C., about 2.1° C., about 2.2° C., about 2.3° C.,about 2.4° C., about 2.5° C., about 2.6° C., about 2.7° C., about 2.8°C., about 2.9° C., about 3° C., about 3.1° C., about 3.2° C., about 3.3°C., about 3.4° C., about 3.5° C., about 3.6° C., about 3.7° C., about3.8° C., about 3.9° C., about 4° C., about 4.1° C., about 4.2° C., about4.3° C., about 4.4° C., about 4.5° C., about 4.6° C., about 4.7° C.,about 4.8° C., about 4.9° C., about 5° C., about 5.1° C., about 5.2° C.,about 5.3° C., about 5.4° C., about 5.5° C., about 5.6° C., about 5.7°C., about 5.8° C., about 5.9° C., about 6° C., about 6.1° C., about 6.2°C., about 6.3° C., about 6.4° C., about 6.5° C., about 6.6° C., about6.7° C., about 6.8° C., about 6.9° C., about 7° C., about 7.1° C., about7.2° C., about 7.3° C., about 7.4° C., about 7.5° C., about 7.6° C.,about 7.7° C., about 7.8° C., about 7.9° C., or about 8° C. Ataccelerated conditions, the enalapril oral liquid formulations describedherein are stable for at least 1 month, at least 2 months, at least 3months, at least 4 months, at least 5 months, at least 6 months, atleast 7 months, at least 8 months, at least 9 months, at least 10months, at least 11 months or at least 12 months. Accelerated conditionsfor the enalapril oral liquid formulations described herein includetemperature and/or relative humidity (RH) that are at or above ambientlevels (e.g. 25±5° C.; 55±10% RH). In some instances, an acceleratedcondition is at about 25° C., about 30° C., about 35° C., about 40° C.,about 45° C., about 50° C., about 55° C. or about 60° C. In otherinstances, an accelerated condition is above 55% RH, about 65% RH, about70% RH, about 75% RH or about 80% RH. In further instances, anaccelerated condition is about 40° C. or 60° C. at ambient humidity. Inyet further instances, an accelerated condition is about 40° C. at 75±5%RH humidity.

Enalapril Oral Powder Formulation

In another aspect, enalapril oral liquid formulations described hereinare prepared from the reconstitution of an enalapril powder formulation.In some embodiments, the enalapril powder formulation comprisingenalapril, a sweetener, a preservative, and optionally an excipient isdissolved in water, a buffer, other aqueous solvent, or a liquid to forman enalapril oral liquid formulation. In one embodiment, the sweeteningagent is sucralose. In one embodiment, the sweetener is not mannitol. Inone embodiment, the sweetening agent is xylitol. In another embodiment,the preservative is sodium benzoate. In one embodiment, the preservativeis a paraben preservative. In one aspect, the enalapril powderformulation described herein comprises enalapril, sucralose, and sodiumbenzoate. In some embodiments, the enalapril powder formulation hereinfurther comprises a flavoring agent. In some embodiments, the enalaprilpowder formulation herein further comprises one or more bufferingagents.

In some embodiments, enalapril or a pharmaceutically acceptable saltthereof, is present in about 0.5% w/w to about 30% w/w of the powderformulation. In other embodiments, enalapril or a pharmaceuticallyacceptable salt thereof, is present in about 0.5 w/w, about 1 w/w, about1.5 w/w, about 2% w/w, about 2.5 w/w, about 3% w/w, about 3.5 w/w, about4% w/w, about 4.5 w/w, about 5 w/w, about 5.5 w/w, about 6% w/w, about6.5 w/w, about 7% w/w, about 7.5 w/w, about 8% w/w, about 8.5 w/w, about9% w/w, about 9.5 w/w, about 10% w/w, about 10.5 w/w, about 11 w/w,about 11.5 w/w, about 12% w/w, about 12.5 w/w, about 13% w/w, about13.5% w/w, about 14% w/w, about 14.5 w/w, about 15 w/w, about 15.5 w/w,about 16% w/w, about 16.5 w/w, about 17% w/w, about 17.5 w/w, about 18%w/w, about 18.5 w/w, about 19% w/w, about 19.5 w/w, about 20% w/w, about20.5 w/w, about 21% w/w, about 21.5 w/w, about 22% w/w, about 22.5 w/w,about 23% w/w, about 23.5 w/w, about 24% w/w, about 24.5 w/w, about w/w,about 25.5 w/w, about 26% w/w, about 26.5 w/w, about 27% w/w, about 27.5w/w, about 28% w/w, about 28.5 w/w, about 29% w/w, about 29.5 w/w, orabout 30% w/w of the powder formulation. In some embodiments, enalaprilor a pharmaceutically acceptable salt thereof, is present in about 10%w/w to about 25 w/w of the powder formulation. In some embodiments,enalapril maleate is present in about 13.5 w/w of the powderformulation. In some embodiments, enalapril maleate is present in about19.5 w/w of the powder formulation. In some embodiments, enalaprilmaleate is present in about 24.5 w/w of the powder formulation. In someembodiments, enalapril is present in about 10.5% w/w of the powderformulation. In some embodiments, enalapril is present in about 14.5%w/w of the powder formulation. In some embodiments, enalapril is presentin about 18% w/w of the powder formulation.

In some embodiments, enalapril or a pharmaceutically acceptable saltthereof, is present in about 0.1% w/w to about 1 w/w of the powderformulation. In other embodiments, enalapril or a pharmaceuticallyacceptable salt thereof, is present in about 0.1% w/w, about 0.15% w/w,about 0.2% w/w, about 0.25% w/w, about 0.3% w/w, about 0.35% w/w, about0.4% w/w, about 0.45% w/w, about 0.5% w/w, about 0.55% w/w, about 0.6%w/w, about 0.65% w/w, about 0.7% w/w, about 0.75% w/w, about 0.8% w/w,about 0.85% w/w, about 0.9% w/w, about 0.95% w/w, or about 1% w/w of thepowder formulation. In some embodiments, enalapril or a pharmaceuticallyacceptable salt thereof, is present in about 0.4% w/w to about 0.7% w/wof the powder formulation. In some embodiments, enalapril maleate ispresent in about 0.45% w/w of the powder formulation. In someembodiments, enalapril maleate is present in about 0.6% w/w of thepowder formulation. In some embodiments, enalapril is present in about0.4% w/w of the powder formulation. In some embodiments, enalapril ispresent in about 0.5% w/w of the powder formulation.

Various amounts and concentrations of other components (sweeteners,buffers, preservatives, and the like) in the enalapril powderformulations are found in the previous section describing the amountsand concentrations for the analogous enalapril oral liquid formulations.For example, in some embodiments where sucralose is present in about 1%w/w to about 30% w/w of the solids in the oral liquid formulation; in ananalogous enalapril powder formulation, sucralose would be about 1 w/wto about 30% w/w in the powder formulation. In some embodiments wheresodium benzoate is present in about 1 w/w to about 30% w/w of the solidsin the oral liquid formulation, in an analogous enalapril powderformulation sodium benzoate is present in about 1 w/w to about 30% w/win the powder formulation.

Liquid vehicles suitable for the enalapril powder formulations to bereconstituted into an oral solution described herein are selected for aparticular oral liquid formulation (solution, suspension, etc.) as wellas other qualities such as clarity, toxicity, viscosity, compatibilitywith excipients, chemical inertness, palatability, odor, color andeconomy. Exemplary liquid vehicles include water, ethyl alcohol,glycerin, propylene glycol, syrup (sugar or other sweetener based, e.g.,Ora-Sweet® SF sugar-free flavored syrup), juices (apple, grape, orange,cranberry, cherry, tomato and the like), other beverages (tea, coffee,soft drinks, milk and the like), oils (olive, soybean, corn, mineral,castor and the like), and combinations or mixtures thereof. Certainliquid vehicles, e.g., oil and water, can be combined together to formemulsions. In some embodiments, water is used for as a vehicle for aenalapril oral liquid formulation. In other embodiments, a syrup is usedfor as a vehicle for a enalapril oral liquid formulation. In yet otherembodiments, a juice is used for as a vehicle for a enalapril oralliquid formulation.

Buffering agents maintain the pH of the liquid enalapril formulation.Non-limiting examples of buffering agents include, but are not limitedto sodium bicarbonate, potassium bicarbonate, magnesium hydroxide,magnesium lactate, magnesium gluconate, aluminum hydroxide, aluminumhydroxide/sodium bicarbonate co precipitate, mixture of an amino acidand a buffer, a mixture of aluminum glycinate and a buffer, a mixture ofan acid salt of an amino acid and a buffer, and a mixture of an alkalisalt of an amino acid and a buffer. Additional buffering agents includecitric acid, sodium citrate, sodium tartrate, sodium acetate, sodiumcarbonate, sodium polyphosphate, potassium polyphosphate, sodiumpyrophosphate, potassium pyrophosphate, disodium hydrogenphosphate,dipotassium hydrogenphosphate, trisodium phosphate, tripotassiumphosphate, sodium acetate, potassium metaphosphate, magnesium oxide,magnesium hydroxide, magnesium carbonate, magnesium silicate, calciumacetate, calcium glycerophosphate, calcium chloride, calcium hydroxide,calcium lactate, calcium carbonate, calcium bicarbonate, and othercalcium salts. Some buffering agents also impart effervescent qualitieswhen a powder is reconstituted in a solution.

In some embodiments, the reconstituted oral liquid formulation comprisesa buffer. In some embodiments, the buffer comprises citric acid andsodium citrate.

In further embodiments, the enalapril powder formulation describedherein comprises additional excipients including, but not limited to,glidants, flavoring agents, coloring agents and thickeners. Additionalexcipients such as bulking agents, tonicity agents and chelating agentsare within the scope of the embodiments.

Glidants are substances that improve flowability of a powder. Suitableglidants include, but are not limited to, calcium phosphate tribasic,calcium silicate, cellulose (powdered), colloidal silicon dioxide,magnesium silicate, magnesium trisilicate, silicon dioxide, starch, talcand the like. In some embodiments, the enalapril powder formulationsdescribed herein comprise a glidant.

In another embodiment, the enalapril powder formulation described hereincomprises a flavoring agent or flavorant to enhance the taste or aromaof the formulation in liquid form. Suitable natural or syntheticflavoring agents can be selected from standard reference books, forexample Fenaroli's Handbook of Flavor Ingredients, 3rd edition (1995).Non-limiting examples of suitable natural flavors, some of which canreadily be simulated with synthetic agents or combinations thereof,include almond, anise, apple, apricot, bergamot, blackberry,blackcurrant, blueberry, cacao, caramel, cherry, cinnamon, clove,coffee, coriander, cranberry, cumin, dill, eucalyptus, fennel, fig,ginger, grape, grapefruit, guava, hop, lemon, licorice, lime, malt,mandarin, molasses, nutmeg, mixed berry, orange, peach, pear,peppermint, pineapple, raspberry, rose, spearmint, strawberry,tangerine, tea, vanilla, wintergreen, etc. Also useful, particularlywhere the formulation is intended primarily for pediatric use, istutti-frutti or bubblegum flavor, a compounded flavoring agent based onfruit flavors. Presently preferred flavoring agents include anise,cinnamon, cacao, orange, peppermint, cherry (in particular wild cherry),grape, bubblegum, vanilla, and mixed berry. Flavoring agents can be usedsingly or in combinations of two or more.

In further embodiments, the enalapril powder formulation describedherein comprises a coloring agent for identity and/or aestheticpurposes. Suitable coloring agents illustratively include FD&C Red No.3, FD&C Red No. 20, FD&C Red No. 40, FD&C Yellow No. 6, FD&C Blue No. 2,D&C Green No. 5, D&C Orange No. 5, caramel, ferric oxide and mixturesthereof.

In further embodiments, the enalapril powder formulation describedherein comprises a thickener. Thickeners impart viscosity or weight tothe resultant liquid forms from the enalapril formulation describedherein. Exemplary thickeners include dextrin, cellulose derivatives(carboxymethylcellulose and its salts, ethylcellulose, hydroxyethylcellulose, methylcellulose, hypromellose, and the like) starches,pectin, polyethylene glycol, polyethylene oxide, trehalose and certaingums (xanthan gum, locust bean gum, etc.).

Additional excipients are contemplated in the enalapril powderformulation embodiments. These additional excipients are selected basedon function and compatibility with the the enalapril powder formulationdescribed herein and may be found, for example in Remington: The Scienceand Practice of Pharmacy, Nineteeth Ed (Easton, Pa.: Mack PublishingCompany, 1995); Hoover, John E., Remington's Pharmaceutical Sciences,(Easton, Pa.: Mack Publishing Co 1975); Liberman, H. A. and Lachman, L.,Eds., Pharmaceutical Dosage Forms (New York, N.Y.: Marcel Decker 1980);and Pharmaceutical Dosage Forms and Drug Delivery Systems, Seventh Ed(Lippincott Williams & Wilkins 1999), herein incorporated by referencein their entirety.

In some embodiments, the enalapril oral liquid formulation prepared fromthe powder formulations described herein are homogenous. Homogenousliquids as used herein refer to those liquids that are uniform inappearance, identity, consistency and drug concentration per volume.Non-homogenous liquids include such liquids that have varied coloring,viscosity and/or aggregation of solid particulates, as well asnon-uniform drug concentration in a given unit volume. Homogeneity inliquids are assessed by qualitative identification or appearance testsand/or quantitative HPLC testing or the like. The mixing methods andexcipients described herein are selected to impart a homogenous qualityto a resultant enalapril oral liquid formulation.

Mixing methods encompass any type of mixing that result in a homogenousenalapril oral liquid formulation. In some embodiments, a quantity of anenalapril powder formulation is added to a liquid vehicle and then mixedby a stirring, shaking, swirling, agitation element or a combinationthereof. In certain instances, a fraction of a enalapril powderformulation (i.e., one-half, one-third, one-fourth, etc.) is added to aliquid vehicle, mixed by stirring, shaking, swirling, agitation or acombination thereof, and the subsequent powder fraction(s) is added andmixed. In other embodiments, a liquid vehicle is added to an enalaprilpowder formulation in a container, for example, a bottle, vial, bag,beaker, syringe, or the like. The container is then mixed by stirring,shaking, swirling, agitation, inversion or a combination thereof. Incertain instances, a fractional volume of the liquid vehicle (i.e.,one-half, one-third, one-fourth volume, etc.) is added to a enalaprilpowder formulation in a container, mixed by stirring, shaking, swirling,agitation, inversion or a combination thereof; and the subsequent liquidfraction(s) is added and mixed. In certain instances, a one-halffractional volume of the liquid vehicle is added to an enalapril powderformulation in a container and mixing by shaking; the other one-halffractional volume of the liquid vehicle is then subsequently added andmixed. In any of the above embodiments, mixing (i.e., stirring, shaking,swirling, agitation, inversion or a combination thereof) occurs for acertain time intervals such as about 10 seconds, about 20 seconds, about30 seconds, about 45 seconds, about 60 seconds, about 90 seconds, about120 seconds, about 2.5 minutes, about 3 minutes, about 3.5 minutes,about 4 minutes, or about 5 minutes. In embodiments, where there are twoor more mixing steps, the time intervals for each mixing can be the same(e.g., 2×10 seconds) or different (e.g., 10 seconds for first mixing and20 seconds for second mixing) In any of the above embodiments, aenalapril oral liquid formulation is allowed to stand for a period oftime such as about 10 minutes, about 20 minutes, about 30 minutes, about45 minutes, about 1 hour, about 1.5 hours or about 2 hours, to allow anyair bubbles resultant from any of the mixing methods to dissipate.

Stability of Enalapril Powder Formulation

The enalapril powder formulations described herein are stable in variousstorage conditions including refrigerated, ambient and acceleratedconditions. Stable as used herein refer to enalapril powder formulationshaving about 95% or greater of the initial enalapril amount and 5% w/wor less total impurities or related substances at the end of a givenstorage period. The percentage of impurities is calculated from theamount of impurities relative to the amount of enalapril. Stability isassessed by HPLC or any other known testing method. In some embodiments,the stable enalapril powder formulations have about 5% w/w, about 4%w/w, about 3% w/w, about 2.5% w/w, about 2% w/w, about 1.5% w/w, about1% w/w, or about 0.5% w/w total impurities or related substances. Inother embodiments, the stable enalapril powder formulations have about5% w/w total impurities or related substances. In yet other embodiments,the stable enalapril powder formulations have about 4% w/w totalimpurities or related substances. In yet other embodiments, the stableenalapril powder formulations have about 3% w/w total impurities orrelated substances. In yet other embodiments, the stable enalaprilpowder formulations have about 2% w/w total impurities or relatedsubstances. In yet other embodiments, the stable enalapril powderformulations have about 1% w/w total impurities or related substances.

At refrigerated and ambient conditions, in some embodiments, theenalapril powder formulations described herein are stable for at least 1week, 2 weeks, 4 weeks, 6 weeks, 8 weeks, 10 weeks, 12 weeks, 16 weeks,20 weeks, at least 24 weeks, at least 30 weeks, or at least 36 weeks. Ataccelerated conditions, in some embodiments, the enalapril powderformulations described herein are stable for at least 1 week, at least 2weeks, at least 3 weeks, at least 4 weeks, at least 5 weeks, at least 6weeks, at least 7 weeks, at least 8 weeks, at least 9 weeks, at least 10weeks, at least 11 weeks or at least 12 weeks. Accelerated conditionsfor the enalapril powder formulations described herein includetemperature and/or relative humidity (RH) that are above ambient levels(e.g. 25±4° C.; 55±10% RH). In some instances, an accelerated conditionis at about 30° C., about 35° C., about 40° C., about 45° C., about 50°C., about 55° C. or about 60° C. In other instances, an acceleratedcondition is above 65% RH, about 70% RH, about 75% RH or about 80% RH.In further instances, an accelerated condition is about 40° C. or 60° C.at ambient humidity. In yet further instances, an accelerated conditionis about 40° C. at 75±5% RH humidity.

Kits and Articles of Manufacture

For the enalapril powder and liquid formulations described herein, kitsand articles of manufacture are also described. Such kits can comprise acarrier, package, or container that is compartmentalized to receive oneor more containers such as vials, tubes, and the like, each of thecontainer(s) comprising one of the separate elements to be used in amethod described herein including an enalapril powder or liquidformulation. Suitable containers include, for example, bottles, vials,syringes, and test tubes. The containers can be formed from a variety ofmaterials such as glass or plastic.

A kit will typically may comprise one or more additional containers,each with one or more of various materials (such as reagents, optionallyin concentrated form, and/or devices) desirable from a commercial anduser standpoint for an enalapril powder or liquid formulation describedherein. Non-limiting examples of such materials include, but not limitedto, buffers, diluents, filters, needles, syringes; carrier, package,container, vial and/or tube labels listing contents and/or instructionsfor use, and package inserts with instructions for use associated withan enalapril powder or liquid formulation. A set of instructions willalso typically be included.

A label can be on or associated with the container. A label can be on acontainer when letters, numbers or other characters forming the labelare attached, molded or etched into the container itself; a label can beassociated with a container when it is present within a receptacle orcarrier that also holds the container, e.g., as a package insert. Alabel can be used to indicate that the contents are to be used for aspecific therapeutic application. The label can also indicate directionsfor use of the contents, such as in the methods described herein.

Methods

Provided herein, in one aspect, are methods of treatment comprisingadministration of the enalapril oral liquid formulations describedherein to a subject. In some embodiments, the enalapril oral liquidformulations described herein treat hypertension in a subject.Hypertension as used herein includes both primary (essential)hypertension and secondary hypertension. In certain instances,hypertension is classified in cases when blood pressure values aregreater than or equal to 140/90 (systolic/diastolic) mm Hg in a subject.In certain instances, the enalapril oral liquid formulations describedherein treat a subject having a blood pressure values are greater thanor equal to 140/90 mm Hg. In certain instances, the enalapril oralliquid formulations described herein treat primary (essential)hypertension in a subject. In other instances, the enalapril oral liquidformulations described herein treat secondary hypertension in a subject.

In other embodiments, the enalapril oral liquid formulations describedherein treat prehypertension in a subject. Prehypertension as usedherein refers to cases where a subject's blood pressure is elevatedabove normal but not to the level considered to be hypertension. In someinstances, prehypertension is classified in cases when blood pressurevalues are 120-139/80-89 mm Hg. In certain instances, the enalapril oralliquid formulations described herein treat a subject having bloodpressure values of 120-139/80-89 mm Hg.

In yet other embodiments, the enalapril oral liquid formulationsdescribed herein are prophylactically administered to subjects suspectedof having, predisposed to, or at risk of developing hypertension. Insome embodiments, the administration of enalapril oral liquidformulations described herein allow for early intervention prior toonset of hypertension. In certain embodiments, upon detection of abiomarker, environmental, genetic factor, or other marker, the enalapriloral liquid formulations described herein are prophylacticallyadministered to subjects.

In further embodiments, the enalapril oral liquid formulations describedherein treat heart failure (e.g., symptomatic congestive), asymptomaticleft ventricular dysfunction, myocardial infarction, diabeticnephropathy and chronic renal failure. In certain instances, theenalapril oral liquid formulations described herein treat symptomaticcongestive heart failure. In other instances, the enalapril oral liquidformulations described herein treat asymptomatic left ventriculardysfunction. In further instances, the enalapril oral liquidformulations described herein treat myocardial infarction. In yetfurther instances, the enalapril oral liquid formulations describedherein treat diabetic nephropathy. In yet further instances, theenalapril oral liquid formulations described herein treat chronic renalfailure.

Dosing

In one aspect, the enalapril oral liquid formulations are used for thetreatment of diseases and conditions described herein. In addition, amethod for treating any of the diseases or conditions described hereinin a subject in need of such treatment, involves administration ofenalapril oral liquid formulations in therapeutically effective amountsto said subject.

Dosages of enalapril oral liquid formulations described can bedetermined by any suitable method. Maximum tolerated doses (MTD) andmaximum response doses (MRD) for enalapril and/or enalaprilat can bedetermined via established animal and human experimental protocols aswell as in the examples described herein. For example, toxicity andtherapeutic efficacy of enalapril and/or enalaprilat can be determinedby standard pharmaceutical procedures in cell cultures or experimentalanimals, including, but not limited to, for determining the LD₅₀ (thedose lethal to 50% of the population) and the ED₅₀ (the dosetherapeutically effective in 50% of the population). The dose ratiobetween the toxic and therapeutic effects is the therapeutic index andit can be expressed as the ratio between LD₅₀ and ED₅₀. Enalaprildosages exhibiting high therapeutic indices are of interest. The dataobtained from cell culture assays and animal studies can be used informulating a range of dosage for use in human. The dosage of suchcompounds lies preferably within a range of circulating concentrationsthat include the ED₅₀ with minimal toxicity. The dosage may vary withinthis range depending upon the dosage form employed and the route ofadministration utilized. Additional relative dosages, represented as apercent of maximal response or of maximum tolerated dose, are readilyobtained via the protocols.

In some embodiments, the amount of a given enalapril oral liquidformulation that corresponds to such an amount varies depending uponfactors such as the particular enalapril salt or form, disease conditionand its severity, the identity (e.g., weight, sex) of the subject orhost in need of treatment, but can nevertheless be determined accordingto the particular circumstances surrounding the case, including, e.g.,the specific agent being administered, the liquid composition type, thecondition being treated, and the subject or host being treated.

In some embodiments, the enalapril oral liquid formulations describedherein are provided in a dose per day from about 0.01 mg to 100 mg, fromabout 0.1 mg to about 80 mg, from about 1 to about 60, from about 2 mgto about 40 mg of enalapril. In certain embodiments, the enalapril oralliquid formulations described herein are provided in a daily dose ofabout 0.01 mg, about 0.05 mg, about 0.1 mg, about 0.2 mg, about 0.4 mg,about 0.6 mg, about 0.8 mg, about 1 mg, about 1.5 mg, about 2 mg, about2.5 mg, about 3 mg, about 4 mg, about 5 mg, about 6 mg, about 7 mg,about 8 mg, about 9 mg, about 10 mg, about 11 mg, about 12 mg, about 15mg, about 20 mg, about 25 mg, about 30 mg, about 35 mg, about 40 mg,about 45 mg, about 50 mg, about 55 mg, about 60 mg, about 65 mg, about70 mg, about 76, mg, about 80 mg, about 85 mg, about 90 mg or about 100mg, or any range derivable therein. In certain instances, the enalapriloral liquid formulations described herein are provided in a dose per dayof about 1 mg. In certain instances, the enalapril oral liquidformulations described herein are provided in a dose per day of about 2mg. In certain instances, the enalapril oral liquid formulationsdescribed herein are provided in a dose per day of about 3 mg. Incertain instances, the enalapril oral liquid formulations describedherein are provided in a dose per day of about 4 mg. In certaininstances, the enalapril oral liquid formulations described herein areprovided in a dose per day of about 5 mg. In certain instances, theenalapril oral liquid formulations described herein are provided in adose per day of about 6 mg. In certain instances, the enalapril oralliquid formulations described herein are provided in a dose per day ofabout 7 mg. In certain instances, the enalapril oral liquid formulationsdescribed herein are provided in a dose per day of about 8 mg. Incertain instances, the enalapril oral liquid formulations describedherein are provided in a dose per day of about 9 mg. In certaininstances, the enalapril oral liquid formulations described herein areprovided in a dose per day of about 10 mg. In certain instances, theenalapril oral liquid formulations described herein are provided in adose per day of about 11 mg. In certain instances, the enalapril oralliquid formulations described herein are provided in a dose per day ofabout 12 mg. The dose per day described herein can be given once per dayor multiple times per day in the form of sub-doses given b.i.d., t.i.d.,q.i.d., or the like where the number of sub-doses equal the dose perday.

In further embodiments, the daily dosages appropriate for the enalapriloral liquid formulations described herein are from about 0.01 to about1.0 mg/kg per body weight. In one embodiment, the daily dosagesappropriate for the enalapril oral liquid formulations are from about0.02 to about 0.8 mg/kg enalapril per body weight. In anotherembodiment, the daily dosage appropriate for the enalapril oral liquidformulations are from about 0.05 to about 0.6 mg/kg per body weight. Inanother embodiment, the daily dosage appropriate for the enalapril oralliquid formulations is about 0.05 mg/kg, about 0.06 mg/kg, about 0.07mg/kg, about 0.08 mg/kg, about 0.10 mg/kg, about 0.15 mg/kg, about 0.20mg/kg, about 0.25 mg/kg, about 0.30 mg/kg, about 0.40 mg/kg, about 0.50mg/kg, or about 0.60 mg/kg.

In other embodiments the enalapril oral liquid formulations are providedat the maximum tolerated dose (MTD) for enalapril and/or enalaprilat. Inother embodiments, the amount of the enalapril oral liquid formulationsadministered is from about 10% to about 90% of the maximum tolerateddose (MTD), from about 25% to about 75% of the MTD, or about 50% of theMTD. In particular embodiments, the amount of the enalapril oral liquidformulations administered is from about 5%, 10%, 15%, 20%, 25%, 30%,35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 99%, orhigher, or any range derivable therein, of the MTD for enalapril and/orenalaprilat.

In further embodiments, the enalapril oral liquid formulations areprovided in a dosage that is similar, comparable or equivalent to adosage of a known enalapril tablet formulation. In other embodiments,the enalapril oral liquid formulations are provided in a dosage thatprovides a similar, comparable or equivalent pharmacokinetic parameters(e.g., AUC, C_(max), T_(max), C_(min), T_(1/2)) as a dosage of a knownenalapril tablet formulation. Similar, comparable or equivalentpharmacokinetic parameters, in some instances, refer to within 80% to125%, 80% to 120%, 85% to 125%, 90% to 110%, or increments therein, ofthe given values. It should be recognized that the ranges can, but neednot be symmetrical, e.g., 85% to 105%.

Administration

Administration of an enalapril oral liquid formulation is at a dosagedescribed herein or at other dose levels and formulations determined andcontemplated by a medical practitioner. In certain embodiments, theenalapril oral liquid formulations described herein are administered forprophylactic and/or therapeutic treatments. In certain therapeuticapplications, the enalapril oral liquid formulations are administered toa patient already suffering from a disease, e.g., hypertension, in anamount sufficient to cure the disease or at least partially arrest orameliorate the symptoms, e.g., lower blood pressure. Amounts effectivefor this use depend on the severity of the disease, previous therapy,the patient's health status, weight, and response to the enalaprilformulations, and the judgment of the treating physician.Therapeutically effective amounts are optionally determined by methodsincluding, but not limited to, a dose escalation clinical trial.

In prophylactic applications, the enalapril oral liquid formulationsdescribed herein are administered to a patient susceptible to orotherwise at risk of a particular disease, e.g., hypertension. Such anamount is defined to be a “prophylactically effective amount or dose.”In this use, the precise amounts also depend on the patient's state ofhealth, weight, and the like. When used in a patient, effective amountsfor this use will depend on the risk or susceptibility of developing theparticular disease, previous therapy, the patient's health status andresponse to the enalapril formulations, and the judgment of the treatingphysician.

In certain embodiments wherein the patient's condition does not improve,upon the doctor's discretion the administration of an enalapril oralliquid formulations described herein are administered chronically, thatis, for an extended period of time, including throughout the duration ofthe patient's life in order to ameliorate or otherwise control or limitthe symptoms of the patient's disease. In other embodiments,administration of an enalapril oral liquid formulation continues untilcomplete or partial response of a disease.

In certain embodiments wherein a patient's status does improve, the doseof an enalapril oral liquid formulation being administered may betemporarily reduced or temporarily suspended for a certain length oftime (i.e., a “drug holiday”). In specific embodiments, the length ofthe drug holiday is between 2 days and 1 year, including by way ofexample only, 2 days, 3 days, 4 days, 5 days, 6 days, 7 days, 10 days,12 days, 15 days, 20 days, 28 days, 35 days, 50 days, 70 days, 100 days,120 days, 150 days, 180 days, 200 days, 250 days, 280 days, 300 days,320 days, 350 days, and 365 days. The dose reduction during a drugholiday is, by way of example only, by 10%400%, including by way ofexample only 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%,70%, 75%, 80%, 85%, 90%, 95%, and 100%.

In some embodiments, enalapril oral liquid formulations described hereinare administered chronically. For example, in some embodiments, anenalapril oral liquid formulation is administered as a continuous dose,i.e., administered daily to a subject. In some other embodiments,enalapril oral liquid formulations described herein are administeredintermittently (e.g. drug holiday that includes a period of time inwhich the formulation is not administered or is administered in areduced amount).

In some embodiments an enalapril oral liquid formulation is administeredto a subject who is in a fasted state. A fasted state refers to asubject who has gone without food or fasted for a certain period oftime. General fasting periods include at least 4 hours, at least 6hours, at least 8 hours, at least 10 hours, at least 12 hours, at least14 hours and at least 16 hours without food. In some embodiments, anenalapril oral liquid formulation is administered orally to a subjectwho is in a fasted state for at least 8 hours. In other embodiments, anenalapril oral liquid formulation is administered to a subject who is ina fasted state for at least 10 hours. In yet other embodiments, anenalapril oral liquid formulation is administered to a subject who is ina fasted state for at least 12 hours. In other embodiments, an enalapriloral liquid formulation is administered to a subject who has fastedovernight.

In other embodiments an enalapril oral liquid formulation isadministered to a subject who is in a fed state. A fed state refers to asubject who has taken food or has had a meal. In certain embodiments, anenalapril oral liquid formulation is administered to a subject in a fedstate 5 minutes post-meal, 10 minutes post-meal, 15 minutes post-meal,20 minutes post-meal, 30 minutes post-meal, 40 minutes post-meal, 50minutes post-meal, 1 hour post-meal, or 2 hours post-meal. In certaininstances, an enalapril oral liquid formulation is administered to asubject in a fed state 30 minutes post-meal. In other instances, anenalapril oral liquid formulation is administered to a subject in a fedstate 1 hour post-meal. In yet further embodiments, an enalapril oralliquid formulation is administered to a subject with food.

In further embodiments described herein, an enalapril oral liquidformulation is administered at a certain time of day for the entireadministration period. For example, an enalapril oral liquid formulationcan be administered at a certain time in the morning, in the evening, orprior to bed. In certain instances, an enalapril oral liquid formulationis administered in the morning. In other embodiments, an enalapril oralliquid formulation can be administered at different times of the day forthe entire administration period. For example, an enalapril oral liquidformulation can be administered on 8:00 am in the morning for the firstday, 12 pm noon for the next day or administration, 4 pm in theafternoon for the third day or administration, and so on.

Further Combinations

The treatment of certain diseases or conditions (e.g., hypertension,heart failure, myocardial infarction and the like) in a subject with anenalapril oral liquid formulation described herein encompass additionaltherapies and treatment regimens with other agents in some embodiments.Such additional therapies and treatment regimens can include anothertherapy, e.g., additional anti-hypertensives, for treatment of theparticular disease or condition in some embodiments. Alternatively, inother embodiments, additional therapies and treatment regimens includeother agents used to treat adjunct conditions associated with thedisease or condition or a side effect from the enalapril oral liquidformulation in the therapy.

Additional agents for use in combination with an enalapril oral liquidformulation described herein include, but are not limited to, diuretics(loop, thiazide, potassium-sparing, and the like), beta blockers(metoprolol, propanolol, pronethalol, and the like), alpha blockers(phentolamine, phenoxybenzamine, tamsulosin, prazosin, and the like),mixed alpha and beta blockers (bucindolol, carvedilol, labetalol),calcium channel blockers (dihydropyridines such as nifedipine,amlodipine, etc., dilitazem, verapamil and the like), angiotensin IIreceptor antagonists (saralasin, lsartan, eprosartin, irbesartan,valsartan, and the like), other ACE inhibitors (captopril, quinapril,ramipril, lisinopril, zofenopril, and the like), aldosterone antagonists(eplerenone, spironolactone and the like), vasodilators (hydralazine andthe like) and alpha-2 agonists (clonidine, moxonidine, guanabenz and thelike).

Certain Definitions

Unless defined otherwise, all technical and scientific terms used hereinhave the same meanings as commonly understood by one of ordinary skillin the art. Although any methods and materials similar or equivalent tothose described herein can be used in the practice or testing ofembodiments described herein, certain preferred methods, devices, andmaterials are now described.

As used herein and in the appended claims, the singular forms “a”, “an”,and “the” include plural reference unless the context clearly dictatesotherwise. Thus, for example, reference to “an excipient” is a referenceto one or more excipients and equivalents thereof known to those skilledin the art, and so forth.

The term “about” is used to indicate that a value includes the standardlevel of error for the device or method being employed to determine thevalue. The use of the term “or” in the claims is used to mean “and/or”unless explicitly indicated to refer to alternatives only or thealternatives are mutually exclusive, although the disclosure supports adefinition that refers to only alternatives and to “and/or.” The terms“comprise,” “have” and “include” are open-ended linking verbs. Any formsor tenses of one or more of these verbs, such as “comprises,”“comprising,” “has,” “having,” “includes” and “including,” are alsoopen-ended. For example, any method that “comprises,” “has” or“includes” one or more steps is not limited to possessing only those oneor more steps and also covers other unlisted steps.

“Optional” or “optionally” may be taken to mean that the subsequentlydescribed structure, event or circumstance may or may not occur, andthat the description includes instances where the events occurs andinstances where it does not.

As used herein, the term “therapeutic” means an agent utilized to treat,combat, ameliorate, prevent or improve an unwanted condition or diseaseof a patient. In some embodiments, a therapeutic agent such as enalaprilis directed to the treatment and/or the amelioration of, reversal of, orstabilization of the symptoms of hypertension described herein.

“Administering” when used in conjunction with a therapeutic means toadminister a therapeutic systemically or locally, as directly into oronto a target tissue, or to administer a therapeutic to a patientwhereby the therapeutic positively impacts the tissue to which it istargeted. Thus, as used herein, the term “administering”, when used inconjunction with an enalapril formulation, can include, but is notlimited to, providing an enalapril formulation into or onto the targettissue; providing an enalapril formulation systemically to a patient by,e.g., oral administration whereby the therapeutic reaches the targettissue or cells. “Administering” a formulation may be accomplished byinjection, topical administration, and oral administration or by othermethods alone or in combination with other known techniques.

The term “animal” as used herein includes, but is not limited to, humansand non-human vertebrates such as wild, domestic and farm animals. Asused herein, the terms “patient,” “subject” and “individual” areintended to include living organisms in which certain conditions asdescribed herein can occur. Examples include humans, monkeys, cows,sheep, goats, dogs, cats, mice, rats, and transgenic species thereof. Ina preferred embodiment, the patient is a primate. In certainembodiments, the primate or subject is a human. In certain instances,the human is an adult. In certain instances, the human is child. Infurther instances, the human is 12 years of age or younger. In certaininstances, the human is elderly. In other instances, the human is 60years of age or older. Other examples of subjects include experimentalanimals such as mice, rats, dogs, cats, goats, sheep, pigs, and cows.The experimental animal can be an animal model for a disorder, e.g., atransgenic mouse with hypertensive pathology. A patient can be a humansuffering from hypertension, or its variants or etiological forms.

By “pharmaceutically acceptable”, it is meant the carrier, diluent orexcipient must be compatible with the other ingredients of theformulation and not deleterious to the recipient thereof.

The term “pharmaceutical composition” shall mean a compositioncomprising at least one active ingredient, whereby the composition isamenable to investigation for a specified, efficacious outcome in amammal (for example, without limitation, a human). Those of ordinaryskill in the art will understand and appreciate the techniquesappropriate for determining whether an active ingredient has a desiredefficacious outcome based upon the needs of the artisan.

A “therapeutically effective amount” or “effective amount” as usedherein refers to the amount of active compound or pharmaceutical agentthat elicits a biological or medicinal response in a tissue, system,animal, individual or human that is being sought by a researcher,veterinarian, medical doctor or other clinician, which includes one ormore of the following: (1) preventing the disease; for example,preventing a disease, condition or disorder in an individual that may bepredisposed to the disease, condition or disorder but does not yetexperience or display the pathology or symptomatology of the disease,(2) inhibiting the disease; for example, inhibiting a disease, conditionor disorder in an individual that is experiencing or displaying thepathology or symptomatology of the disease, condition or disorder (i.e.,arresting further development of the pathology and/or symptomatology),and (3) ameliorating the disease; for example, ameliorating a disease,condition or disorder in an individual that is experiencing ordisplaying the pathology or symptomatology of the disease, condition ordisorder (i.e., reversing the pathology and/or symptomatology). As such,a non-limiting example of a “therapeutically effective amount” or“effective amount” of a formulation of the present disclosure may beused to inhibit, block, or reverse the activation, migration, orproliferation of cells or to effectively treat hypertension orameliorate the symptoms of hypertension.

The terms “treat,” “treated,” “treatment,” or “treating” as used hereinrefers to both therapeutic treatment in some embodiments andprophylactic or preventative measures in other embodiments, wherein theobject is to prevent or slow (lessen) an undesired physiologicalcondition, disorder or disease, or to obtain beneficial or desiredclinical results. For the purposes described herein, beneficial ordesired clinical results include, but are not limited to, alleviation ofsymptoms; diminishment of the extent of the condition, disorder ordisease; stabilization (i.e., not worsening) of the state of thecondition, disorder or disease; delay in onset or slowing of theprogression of the condition, disorder or disease; amelioration of thecondition, disorder or disease state; and remission (whether partial ortotal), whether detectable or undetectable, or enhancement orimprovement of the condition, disorder or disease. Treatment includeseliciting a clinically significant response without excessive levels ofside effects. Treatment also includes prolonging survival as compared toexpected survival if not receiving treatment. A prophylactic benefit oftreatment includes prevention of a condition, retarding the progress ofa condition, stabilization of a condition, or decreasing the likelihoodof occurrence of a condition. As used herein, “treat,” “treated,”“treatment,” or “treating” includes prophylaxis in some embodiments.

Examples Example A: Effect of pH on the Formation of Degradants inEnalapril Formulations at 60° C.

Formulations were prepared containing enalapril maleate according toTable A-1. The pH of each solution was recorded. Five milliliters ofeach formulation were transferred to each of four 3-dram glassscrew-capped vials with Teflon inserts in the caps. The vials wereplaced into a 60° C. heating chamber then one vial removed and analyzedby HPLC at times of zero, ˜97 and ˜180 hours.

TABLE A-1 Formulation (in mg/mL) of Enalapril Formulations at Varying pHand Citrate Buffer Concentration Formulation (mM citrate) A1 A2 A3 A4 A5A6 Component (50) (50) (50) (50) (50) (25) Enalapril maleate 1.0 1.0 1.01.0 1.0 1.0 Mannitol 50 50 50 50 6.0 Xylitol 50 Citric acid, 7.35 5.052.55 5.05 5.05 2.76 anhydrous Sodium citrate, 3.45 7.0 10.8 7.0 7.0 3.15dihydrate Sodium benzoate 1 1 1 1 1 Methylparaben sodium 1.75 0.335Propylparaben sodium 0.095 Potassium sorbate 1 Sucralose 0.75 0.75 0.750.75 0.75 0.75 Silicon dioxide 0.075 Mixed berry flavor 0.5 0.5 0.5 0.50.5 0.5 (powdered) Water qs qs qs qs qs qs pH 3.4 4.4 5.2 4.4 4.5 4.4 qs= sufficient quantity

The results of the HPLC analysis for the two main degradants in thesamples, enalapril diketopiperazine and enalaprilat, are provided inTable A-2.

TABLE A-2 Primary Degradants Present in the Formulations (% w/w ofenalapril maleate) Hours at Formulation 60° C. A1 A2 A3 A4 A5 A6Enalapril Diketopiperazine 0 0.04 0.03 0.03 0.03 0.03 0.03 97 3.10 0.880.33 0.86 0.70 0.53 180 6.21 1.77 0.75 1.73 1.43 1.07 Enalaprilat 0 0.090.15 0.29 0.14 0.16 0.12 97 5.20 16.9 47.4 16.1 20.3 15.6 180 9.94 34.8113 33.5 42.2 31.7

Example B: Effect of Buffer Concentration on the Formation of Degradantsin Enalapril Formulations at 60° C.

Formulations were prepared containing enalapril maleate according toTable B-1. The pH of each solution was measured and adjusted as neededto pH 3.3 with ˜1N HCl or ˜0.5N NaOH. Five milliliters of eachformulation were transferred to each of six 3-dram glass screw-cappedvials with Teflon inserts in the caps. The vials were placed into a 60°C. heating chamber then two vials were removed and analyzed by HPLC attimes of zero, ˜66 and ˜139 hours.

TABLE B-1 Formulation (in mg/mL) of Enalapril Maleate Formulations atVarying Citrate Buffer Concentrations Formulation B1 (5 mM B2 (10 mM B3(20 mM Component citrate) citrate) citrate) Enalapril maleate 1.0 1.01.0 Citric acid, anhydrous 0.82 1.65 3.29 Sodium citrate, anhydrous 0.190.38 0.75 Sodium benzoate 1.0 1.0 1.0 Sucralose 0.7 0.7 0.7 Mixed berryflavor (powdered) 0.5 0.5 0.5 Water qs qs qs pH 3.3 3.3 3.3 qs =sufficient quantity

The results of the HPLC analysis for the two main degradants in thesamples, enalapril diketopiperazine and enalaprilat, are provided inTable B-2.

TABLE B-2 Primary Degradants Present in the Formulations (% w/w ofenalapril maleate) Hours Formulation at 60° C. B1 (5 mM citrate) B2 (10mM citrate) B3 (20 mM citrate) Enalapril Diketopiperazine 0 0.01 0.010.01 66 1.57 1.63 1.79 139 3.70 3.94 4.24 Enalaprilat 0 0.00 0.00 0.0066 2.98 2.88 3.19 139 5.28 5.23 5.69

Example C: Stability of Enalapril Maleate Formulations ContainingParaben Preservatives

Powder formulations were prepared according to Table C-1. All componentsin each formulation except mannitol or xylitol were added to a 2.5 literpolypropylene screw capped bottle. The bottle was mixed by inversion ina Turbula® mixer for 5 minutes. The mannitol or xylitol was then addedand the components mixed for 5 minutes, then the other half of themannitol or xylitol was added and a final mix of 5 minutes wascompleted.

One liter of solution formulation was prepared for each formulation byadding an appropriate amount of each powdered formulation to a 1 litervolumetric flask and adding about 500 mL water. The powder was dissolvedwith mixing then the contents of the flask were brought to 1 liter withadditional water. The amount of powder to add was determined such thatthe final concentration of enalapril maleate was 1.0 mg/mL. Fiftymilliliter aliquots of each formulation were placed into HDPE bottles.The bottles were screw-capped and placed into storage at 5° C.±3° C., atroom temperature (19-23° C.) and at 40° C.±2° C. At various times,bottles were removed from the storage condition and analyzed.

TABLE C-1 Composition of Enalapril Maleate Formulations Component C1 C2C3 C4 C5 Powder Formulation (grams) Enalapril maleate 12.3 12.3 8.862.16 2.16 Mannitol 74.4 74.4 394.0 Xylitol 96.6 93.7 Citric acid,anhydrous 28.6 35.6 28.4 5.40 5.40 Sodium citrate, 24.5 14.7 7.73 4.104.10 anhydrous Sodium methylparaben 4.17 4.17 8.86 2.16 2.16 Sodiumpropylparaben 1.10 1.10 Potassium sorbate 12.3 12.3 Sodium benzoate 8.862.16 2.16 Xanthan Gum 1.62 Colloidal silicon dioxide 0.859 0.859 4.431.08 Sucralose 9.20 9.20 6.64 1.62 1.62 Mixed berry flavor 6.13 6.134.43 1.08 1.08 Total solids 173.5 170.7 472.3 115.2 115.2 LiquidFormulations (mg/mL) Enalapril maleate 1.00 1.00 1.00 1.00 1.00 Mannitol6.07 6.07 44.5 Xylitol 44.7 43.4 Citric acid, anhydrous 2.33 2.90 3.212.50 2.50 Sodium citrate, 2.00 1.20 0.87 1.90 1.90 anhydrous Sodiummethylparaben 0.34 0.34 1.00 1.00 1.00 Sodium propylparaben 0.09 0.091.00 Potassium sorbate 1.00 1.00 Sodium benzoate 1.00 1.00 1.00 XanthanGum 0.75 Colloidal silicon dioxide 0.07 0.07 0.50 0.50 Sucralose 0.750.75 0.75 0.75 0.75 Mixed berry flavor 0.50 0.50 0.50 0.50 0.50 pH(measured) 4.4 3.8 3.7 4.4 4.6

The results of the HPLC analysis for the diketopiperazine andenalaprilat degradants in the samples are provided in Table C-2.

TABLE C-2 Degradant Content After Storage (% w/w of enalapril maleate)Storage Formulation ° C. Weeks C1 C2 C3 C4 C5 Liquid FormulationsDiketo-  5 0 0.03 0.04 0.04 0.02 0.02 piperazine 4 0.02 0.03 0.03 0.030.02 8 0.03 0.04 0.04 19-23 0 0.03 0.04 0.04 0.02 0.02 4 0.05 0.09 0.110.05 0.04 8 0.08 0.17 0.19 40 0 0.03 0.04 0.04 0.02 0.02 4 0.35 0.911.10 0.31 0.21 8 0.65 1.80 2.05 Enalaprilat  5 0 0.18 0.14 0.12 0.130.19 4 0.18 0.15 0.12 0.43 0.53 8 0.55 0.38 0.34 19-23 0 0.18 0.14 0.120.13 0.19 4 1.35 0.83 0.80 1.75 2.29 8 3.34 2.06 1.98 40 0 0.18 0.140.12 0.13 0.19 4 10.49 6.08 6.11 12.30 16.14 8 24.37 14.12 14.22

Example D: Stability of Enalapril Maleate Formulations ContainingBenzoate Preservative

Powder formulations were prepared according to Table D-1. All componentsin each formulation except enalapril maleate and mannitol or xylitolwere blended with a mortar and pestle. The enalapril maleate was thentriturated with the blend. The xylitol or mannitol was then trituratedinto the blend using a geometric dilution technique.

One liter of solution formulation was prepared for each formulation byadding an appropriate amount of each powdered formulation to a 1 litervolumetric flask and adding about 500 mL water. The powder was dissolvedwith mixing then the contents of the flask were brought to 1 liter withadditional water. The amount of powder to add was determined such thatthe final concentration of enalapril maleate was 1.0 mg/mL. Fiftymilliliter aliquots of each formulation were placed into HDPE bottles.The bottles were screw-capped and placed into storage at 5° C.±3° C., atroom temperature (19-23° C.) and at 40° C.±2° C. At various times,bottles were removed from the storage condition and analyzed.

TABLE D-1 Composition of Enalapril Maleate Formulations Component D1 D2D3 D4 D5 D6 Powder Formulation (grams) Enalapril 3.63 3.63 3.63 3.638.86 2.16 maleate Xylitol 537.2 176.1 537.2 Mannitol 319.4 401.2 98.9Citric acid, 11.9 11.9 11.9 10.4 26.6 6.48 anhydrous Sodium citrate,2.72 2.72 2.72 4.86 11.3 2.76 anhydrous Sodium 3.63 3.63 3.63 3.63 8.862.16 benzoate Rebalance X60 10.9 (sucralose and maltodextrin) Sucralose6.64 1.62 Saccharin 7.26 sodium Colloidal 4.43 silicon dioxide Mixedberry 1.82 1.82 1.82 1.82 4.43 1.08 flavor Total solids 561 211 350. 561472.3 115.2 Liquid Formulations (mg/mL) Enalapril 1.00 1.00 1.00 1.001.00 1.00 maleate Xylitol 148.0 48.5 148.0 Mannitol 88.0 45.3 45.8Citric acid, 3.29 3.29 3.29 2.85 3.00 3.00 anhydrous Sodium citrate,0.75 0.75 0.75 1.34 1.28 1.28 anhydrous Sodium 1.00 1.00 1.00 1.00 1.001.00 benzoate Rebalance X60 3.00 (sucralose and maltodextrin) Sucralose0.75 0.75 Saccharin 2.00 sodium Colloidal 0.50 silicon dioxide Mixedberry 0.50 0.50 0.50 0.50 0.50 0.50 flavor pH (measured) 3.2 3.2 3.4 3.73.6 3.6

The results of the HPLC analysis for the diketopiperazine andenalaprilat degradants in the samples are provided in Table D-2.

TABLE D-2 Degradant Content After Storage (% w/w of enalapril maleate)Storage Formulation ° C. Weeks D1 D2 D3 D4 D5 D6 Liquid FormulationsDiketo-  5 0 0.04 0.02 0.03 0.03 0.04 0.04 piperazine 4 0.07 0.03 0.050.05 0.03 8 0.11 0.06 0.08 0.08 0.05 12 0.08 0.04 0.06 0.06 26 0.11 0.070.09 0.07 19-23 0 0.04 0.02 0.03 0.03 0.04 0.04 4 0.27 0.21 0.24 0.160.12 0.12 8 0.50 0.41 0.47 0.30 0.21 0.22 12 0.62 0.52 0.58 0.35 26 1.391.20 1.33 0.76 40 0 0.04 0.02 0.03 0.03 0.04 0.04 4 2.87 2.32 2.73 1.571.21 1.13 8 5.13 4.42 5.44 2.97 2.23 2.16 12 6.86 5.90 6.90 3.91 2613.63 12.18 13.56 7.74 Enalaprilat  5 0 0.03 0.02 0.03 0.03 0.13 0.14 40.15 0.12 0.06 0.17 0.13 8 0.22 0.19 0.22 0.27 0.34 12 0.20 0.17 0.190.22 8 0.32 0.30 0.30 0.39 19-23 0 0.03 0.02 0.03 0.03 0.13 0.14 4 0.690.66 0.69 0.86 0.74 0.76 8 1.38 1.33 1.41 1.68 1.83 1.82 12 1.71 1.681.73 2.15 26 3.63 3.61 3.59 4.55 40 0 0.03 0.02 0.03 0.03 0.13 0.14 44.76 4.42 4.76 6.45 5.55 5.24 8 8.95 8.64 9.61 12.94 12.73 12.18 1211.01 10.64 11.41 16.16 26 17.18 17.11 18.30 27.36

Example E: Stability of Solution Formulations of Enalapril Maleate

Solution formulations were prepared according to Table E-1. Thirtymilliliter aliquots of each formulation were placed into HDPE bottles.The bottles were screw-capped and placed into storage at 5° C.±3° C., atroom temperature (19-23° C.) and at 40° C.±2° C. At various times,bottles were removed from the storage condition and analyzed.

Composition of Enalapril Maleate Formulations (mg/mL) Component E1 E2 E3E4 E5 E6 Enalapril maleate 1.00 1.00 1.00 1.00 1.00 1.00 Xylitol 150 200150 Citric acid anhydrous 3.29 3.29 3.29 3.29 1.65 0.82 Sodium citrate0.75 0.75 0.75 0.75 0.38 0.19 anhydrous Sodium benzoate 1.00 1.00 1.001.00 1.00 1.00 Sucralose 0.70 0.70 0.70 Mixed berry flavor 0.50 0.500.50 0.50 0.50 Water qs qs qs qs qs qs pH (measured) 3.3 3.3 3.3  3.43.3  3.3  qs = sufficient quantity

The results of the HPLC analysis for the diketopiperazine andenalaprilat degradants in the samples are provided in Table E-2.

TABLE E-2 Degradant Content After Storage (% w/w of enalapril maleate)Storage Formulation ° C. Weeks E1 E2 E3 E4 E5 E6 Diketo-  5 0 0.01 0.010.01 0.01 0.01 0.01 piperazine 4 0.04 0.04 0.05 0.04 0.03 0.03 8 0.040.04 0.04 0.04 0.03 0.03 12 0.05 0.05 0.04 0.05 0.04 0.04 26 0.07 0.060.05 0.06 0.05 0.05 52 0.15 0.14 62 0.18 0.18 0.16 0.14 19-23 0 0.010.01 0.01 0.01 0.01 0.01 4 0.22 0.23 0.21 0.20 0.16 0.15 8 0.35 0.350.32 0.31 0.29 0.28 12 0.58 0.59 0.53 0.51 0.48 0.45 26 1.10 1.10 1.000.95 0.97 0.92 52 2.30 2.15 62 3.02 3.04 2.75 2.64 40 0 0.01 0.01 0.010.01 0.01 0.01 4 2.65 2.71 2.60 2.42 1.76 1.68 8 4.02 3.99 3.99 3.623.37 3.13 12 6.72 6.42 6.47 6.00 5.53 5.29 Enalaprilat  5 0 0.00 0.000.01 0.02 0.00 0.00 4 0.07 0.09 0.10 0.11 0.07 0.08 8 0.12 0.14 0.100.13 0.09 0.08 12 0.16 0.15 0.15 0.17 0.14 0.11 26 0.31 0.30 0.29 0.310.27 0.24 52 0.54 0.46 62 0.75 0.75 0.74 0.71 19-23 0 0.00 0.00 0.010.02 0.00 0.00 4 0.65 0.65 0.68 0.70 0.50 0.46 8 1.17 1.19 1.20 1.231.03 0.95 12 1.67 1.69 1.72 1.80 1.30 1.21 26 3.36 3.38 3.42 3.57 3.072.90 52 6.32 5.88 62 7.99 8.02 8.04 8.57 40 0 0.00 0.00 0.01 0.02 0.000.00 4 4.85 4.93 5.19 5.42 3.33 3.25 8 8.08 8.06 8.56 9.01 6.65 6.35 1210.70 10.48 11.01 11.97 8.14 7.96

Example F: Effect of pH on the Formation of Degradants in EnalaprilFormulations at 5° C. and 19-23° C.

The content of enalapril diketopiperazine and enalaprilat that wereformed after 8 weeks of storage for formulations C1-C3 and D1-D5 areplotted in FIG. 1 (5° C.±3° C.) and FIG. 2 (19-23° C. storage). Theseformulations all contained 20 mM total citrate buffer content, but withvarying pH. The general effects of formulation pH on the formation ofthe two main enalapril degradants are shown.

Example G: Antimicrobial Effectiveness Testing of Enalapril MaleateFormulations at pH 3.3

Enalapril formulations were prepared containing differing amounts of theantimicrobial preservative, sodium benzoate. The formulations were thentested for antimicrobial effectiveness (AET) according to the proceduresin the 2014 United States Pharmacopeia 37, Chapter <51> for category 3products. The formulation of the formulations and the AET results areincluded in Table G-1.

TABLE G-1 Formulation and AET Testing Results Formulation G1 G2 G3 G4 G5Formulation (mg/mL) Enalapril maleate 1.00 1.00 1.00 1.00 1.00 Xylitol150 150 150 150 Sucralose 0.70 Citric acid, anhydrous 1.64 1.64 1.641.64 1.80 Sodium citrate, anhydrous 0.322 0.322 0.322 0.322 Sodiumcitrate, dihydrate 0.165 Sodium benzoate 1.00 0.80 0.60 0.40 1.0 Mixedberry flavor 0.50 0.50 0.50 0.50 0.50 Water q.s. q.s. q.s. q.s. q.s.HCl/NaOH as need to achieve pH Measured pH 3.3 3.3 3.3 3.3 3.3 AETResults USP <51> Pass Pass Pass Pass Pass qs = sufficient quantity

Example H: Clinical Trial: Bioavailability Study of 10 mg EnalaprilMaleate Oral Solution Vs. 10 mg Epaned® Powder for Oral Solution(Reconstituted) Under Fasted Conditions

The objective of this open-label, randomized, two-period, two-treatment,two-way crossover study was to compare the oral bioavailability of atest formulation of 10 mL of enalapril maleate oral solution, 1 mg/mL(formulation E-5), to an equivalent oral dose of the commerciallyavailable comparator product, Epaned® (enalapril maleate) Powder forOral Solution, 1 mg/mL, when administered under fasted conditions inhealthy adults.

Study design: Thirty-two healthy adult subjects received a single 10 mLdose of enalapril maleate oral solution, 1 mg/mL, formulation E-5(Treatment A), in one period and a separate single dose of Epaned Powderfor Oral Solution (reconstituted with the supplied Ora-Sweet SF), 1mg/mL (Treatment B) in another period. Each treatment was administeredafter an overnight fast of at least 10 hours, followed by a 4-hour fastpostdose. Each treatment was administered via a 10 mL oral dosingsyringe and followed with 240 mL of room temperature tap water. Eachdrug administration was separated by a washout period of at least 7days.

During each study period, meals were the same and scheduled atapproximately the same times relative to dose. In addition, during eachperiod, blood samples were obtained prior to and following each dose atselected times through 72 hours postdose. Pharmacokinetic samples wereanalyzed for enalapril and its metabolite enalaprilat using a validatedanalytical method; appropriate pharmacokinetic parameters werecalculated for each formulation using non-compartmental methods. Bloodwas also drawn and urine collected for clinical laboratory testing atscreening and at the end of the study.

Statistical Methods: The concentration-time data were analyzed usingnoncompartmental methods in Phoenix™ WinNonlin® (Version 6.3, PharsightCorporation). Concentration-time data that were below the limit ofquantitation (BLQ) were treated as zero in the data summarization anddescriptive statistics. In the pharmacokinetic analysis, BLQconcentrations were treated as zero from time-zero up to the time atwhich the first quantifiable concentration was observed; embedded and/orterminal BLQ concentrations were treated as “missing”. Actual sampletimes were used for all pharmacokinetic and statistical analyses.Analysis of variance (ANOVA) and the Schuirmann's two one-sided t-testprocedures at the 5% significance level were applied to thelog-transformed pharmacokinetic exposure parameters, C_(max),AUC_(last), and AUC_(inf). The 90% confidence interval for the ratio ofthe geometric means (Test/Reference) was calculated. Bioequivalence wasdeclared if the lower and upper confidence intervals (CIs) of thelog-transformed parameters were within 80% to 125% for enalapril andenalaprilat.

Results: A total of 32 subjects participated in the study and 29 ofthese subjects completed both study periods. Based on the geometric meanratios of enalapril and enalaprilat AUCs (AUC_(last) and AUC_(inf)), thebioavailability of the enalapril maleate oral solution (formulation E-5)relative to the Epaned Powder for Oral Solution (reconstituted) wasapproximately 105% to 110%. The geometric mean ratios of enalapril andenalaprilat C_(max) were approximately 115% and 109%, respectively. The90% CI for comparing the maximum exposure to enalapril and enalaprilat,based on ln (C_(max)), was within the accepted 80% to 125% limits. The90% CIs for comparing total systemic exposure to enalapril andenalaprilat, based on ln (AUC_(last)) and ln (AUC_(inf)), was within theaccepted 80% to 125% limits. Therefore, the test formulation ofenalapril maleate oral solution, 1 mg/mL, is bioequivalent to thereference product, Epaned Powder for Oral Solution (reconstituted), 1mg/mL, under fasted conditions.

While preferred embodiments of the present invention have been shown anddescribed herein, it will be obvious to those skilled in the art thatsuch embodiments are provided by way of example only. Numerousvariations, changes, and substitutions will now occur to those skilledin the art without departing from the invention. It should be understoodthat various alternatives to the embodiments of the invention describedherein may be employed in practicing the invention. It is intended thatthe following claims define the scope of the invention and that methodsand structures within the scope of these claims and their equivalents becovered thereby.

What is claimed is:
 1. A method of treating hypertension in a subjectcomprising administering to that subject a therapeutically effectiveamount of a stable oral liquid formulation comprising: (i) about 1 mg/mlenalapril maleate; (ii) a buffer comprising about 1.82 mg/ml citric acidand about 0.15 mg/ml sodium citrate dihydrate; (iii) about 1 mg/ml of apreservative that is sodium benzoate; and (iv) water; wherein the pH ofthe stable oral liquid formulation is less than about 3.5; wherein thestable oral liquid formulation is stable at about 5±3° C. for at least12 months; and wherein the stable oral liquid formulation has about 95%or greater of the initial enalapril amount and about 5% w/w or lesstotal impurities or related substances at the end of the given storageperiod.
 2. The method of claim 1, wherein the stable oral liquidformulation further comprises a flavoring agent.
 3. The method of claim1, wherein the stable oral liquid formulation further comprises about0.70 mg/ml of a sweetener that is sucralose.
 4. The method of claim 1,wherein the pH is between about 3 and about 3.5.
 5. The method of claim1, wherein the pH is about 3.3.
 6. The method of claim 1, wherein thecitrate concentration in the buffer is about 5 mM to about 20 mM.
 7. Themethod of claim 1, wherein the citrate concentration in the buffer isabout 10 mM.
 8. The method of claim 1, wherein the stable oral liquidformulation is stable at about 5±3° C. for at least 18 months.
 9. Themethod of claim 1, wherein the stable oral liquid formulation is stableat about 5±3° C. for at least 24 months.
 10. The method of claim 1,wherein the stable oral liquid formulation does not contain mannitol orsilicon dioxide.
 11. The method of claim 1, wherein the hypertension isprimary (essential) hypertension.
 12. The method of claim 1, wherein thehypertension is secondary hypertension.
 13. The method of claim 1,wherein the subject has blood pressure values greater than or equal to140/90 mmm Hg.
 14. The method of claim 1, wherein the subject is elderlyor a child.
 15. The method of claim 1, wherein the stable oral liquidformulation is further administered in combination with an agentselected from the group consisting of diuretics, beta blockers, alphablockers, mixed alpha and beta blockers, calcium channel blockers,angiotensin II receptor antagonists, ACE inhibitors, aldosteroneantagonists, and alpha-2 agonists.
 16. A method of treating heartfailure in a subject comprising administering to that subject atherapeutically effective amount of a stable oral liquid formulationcomprising: (i) about 1 mg/ml enalapril maleate; (ii) a buffercomprising about 1.82 mg/ml citric acid and about 0.15 mg/ml sodiumcitrate dihydrate; and (iii) about 1 mg/ml of a preservative that issodium benzoate; and (iv) water; wherein the pH of the stable oralliquid formulation is less than about 3.5; wherein the stable oralliquid formulation is stable at about 5±3° C. for at least 12 months;and wherein the stable oral liquid formulation has about 95% or greaterof the initial enalapril amount and about 5% w/w or less totalimpurities or related substances at the end of the given storage period.17. The method of claim 16, wherein the stable oral liquid formulationfurther comprises about 0.70 mg/ml of a sweetener that is sucralose. 18.The method of claim 16, wherein the pH is between about 3 and about 3.5.19. The method of claim 16, wherein the pH is between about 3.3.
 20. Themethod of claim 16, wherein the citrate concentration in the buffer isabout 5 mM to about 20 mM.
 21. The method of claim 16, wherein thestable oral liquid formulation is stable at about 5±3° C. for at least24 months.
 22. The method of claim 16, wherein the stable oral liquidformulation does not contain mannitol or silicon dioxide.
 23. The methodof claim 16, wherein the heart failure is congestive heart failure. 24.A method of treating left ventricular dysfunction in a subjectcomprising administering to that subject a therapeutically effectiveamount of a stable oral liquid formulation comprising: (i) about 1 mg/mlenalapril maleate; (ii) a buffer comprising about 1.82 mg/ml citric acidand about 0.15 mg/ml sodium citrate dihydrate; and (iii) about 1 mg/mlof a preservative that is sodium benzoate; and (iv) water; wherein thepH of the stable oral liquid formulation is less than about 3.5; whereinthe stable oral liquid formulation is stable at about 5±3° C. for atleast 12 months; and wherein the stable oral liquid formulation hasabout 95% or greater of the initial enalapril amount and about 5% w/w orless total impurities or related substances at the end of the givenstorage period.
 25. The method of claim 24, wherein the stable oralliquid formulation further comprises about 0.70 mg/ml of a sweetenerthat is sucralose.
 26. The method of claim 24, wherein the pH is betweenabout 3 and about 3.5.
 27. The method of claim 24, wherein the pH isbetween about 3.3.
 28. The method of claim 24, wherein the citrateconcentration in the buffer is about 5 mM to about 20 mM.
 29. The methodof claim 24, wherein the stable oral liquid formulation is stable atabout 5±3° C. for at least 24 months.
 30. The method of claim 24,wherein the stable oral liquid formulation does not contain mannitol orsilicon dioxide.